Editor's note: Editor's note: This account of the 24 hours leading to the capture of the last of the marathon bombing suspects is based on CNN reporting, including interviews with witnesses and law enforcement. The story also contains information from verified Twitter accounts. A few details from other media outlets are attributed to those sources.
Watertown, Massachusetts (CNN) -- The black Mercedes SUV sped down Spruce Street going about 70 mph, the driver struggling to maintain control. The vehicle had a busted headlight and flat tire.
With each rotation of its tire, the SUV made a loud thud -- whop, whop, whop. Gunshots and sirens from police cars in pursuit added to the soundtrack echoing across the neighborhood.
Residents of this sleepy Boston suburb were rattled awake.
Max Kerman, once a football and basketball star at Watertown high, rushed outside from his second-floor bedroom. For sure, he thought, cars parked along the narrow street would get smashed.
Gunshots continued to ring out. It appeared the driver of the SUV was shooting at cops. Kerman hit the ground and dialed 911. He didn't get an answer, so he dialed again.
He was told to stay put. Officers in cars slowed at the top of the street where the road hooks.
"Keep going!" Kerman shouted. "Keep going!"
It was the early hours of Friday, April 19.
Just up the road, the driver ditched the stolen car and disappeared into the dark of night.
One of the largest manhunts in the nation's history was hurtling toward a conclusion after paralyzing a city and captivating the nation. Two brothers, Dzhokhar Tsarnaev, 19, and Tamerlan Tsarnaev, 26, would become known as the suspects in the Boston Marathon bombings that killed three people and wounded 264 others.
Plenty of questions remain about what might have motivated them. Where were they and what were they doing in the weeks and months before the bombings? Answers to those questions are still emerging. What is clear is the 24 hours that ended in one brother's death and the other's capture.
Details reveal a remarkable collaboration between law enforcement and the public.
A cop killing and carjacking
The city of Cambridge was best known for its multiculturalism and astute intellectuals who attended Harvard and the Massachusetts Institute of Technology. It was not your typical terror breeding ground.
Officer Sean Collier sat alone in his patrol car last Thursday around 10:30 p.m. The New York Times reported that an ambulance staffed with students had rolled by shortly before. He flashed his blue lights to say hi; they responded with red lights, according to the Times.
The 27-year-old officer was wearing a protective vest. Five hours earlier, the FBI had released photographs and surveillance video of the two marathon bombing suspects, hoping the public could identify them. Authorities were told to be extra vigilant.
Collier didn't have time to react when two men approached from behind, shooting. He was struck four to five times.
It took 13 minutes to reach the downed officer after 911 calls reported shots fired. Enough time for the suspects to get away.
"That is confirmed, a gunshot wound. CPR in progress," one first responder radioed back.
Collier was rushed to Massachusetts General Hospital where he was pronounced dead, making him the fourth fatality in the carnage in Boston.
Across the Charles River, several blocks from the shooting scene, a man who authorities believe was Tamerlan Tsarnaev approached a black Mercedes ML 350 SUV in the Allston neighborhood and tapped on the passenger window. The driver rolled down the window and the suspect reached inside, opened the door and brandished his handgun.
"Did you hear about the Boston explosion?" he said, according to an affidavit. "I did that."
He pulled the magazine from his weapon and showed he was loaded. "I am serious," he said.
The driver told the Boston Globe it was the start of a terrifying 90-minute odyssey across metro Boston, first with the younger brother trailing in a second car, before stopping in a neighborhood in East Watertown. It was there, the driver said, the two men transferred heavy objects into the Mercedes.
"Luggage," the driver thought, according to the Globe.
The younger brother, Dzhokhar, hopped in the back seat. Tamerlan took over the driving.
"They asked me where I'm from. I told them I'm Chinese," the carjacking victim told CNN-affiliate WMUR. "I asked them if they were going to hurt me. They said they won't hurt me. I was thinking, 'I think they will kill me later.'"
The man with the gun demanded cash. The carjacking victim handed over $45. They wanted more money so he gave them his ATM card and the passcode. Dzhokhar was seen on surveillance video at a Bank of America ATM at 11:18 p.m.
Both brothers were said to love high-end cars, and now they were in a carjacked Mercedes darting from Allston to Watertown to Cambridge. Eventually, the fuel tank neared empty.
The brothers mentioned something about New York as they drove, according to the driver. Authorities have since said the two planned to attack Times Square.
The Mercedes pulled into a Shell gas station on Memorial Drive. Dzhokhar went inside to pay. According to the Boston Globe, Tamerlan put his gun in the door pocket to fiddle with a navigation system.
The carjacking victim saw this as his opportunity to flee. "I jumped out of the car and ran away across the street," he told WMUR.
Tamerlan tried to grab him, "but I ran very fast." He could hear the man swearing as he sprinted for his life.
"It was very scary at that moment," he recalled. "For me, I'm so lucky."
He burst through the door of a nearby Mobil gas station so hard, the clerk was angry -- until he saw the panic on the man's face and heard his pleas to call police. The carjacking victim curled up in a back room and hid.
The men in the stolen SUV sped off.
Somewhere along the way, the two stopped to pick up their other car: a green Honda Civic with a Massachusetts tag 116GC7. Earlier in the day, authorities had put out an all-points bulletin for that exact vehicle.
A dramatic shootout in Watertown
"Heading to Watertown," the voice said over police dispatch.
Two hours had passed since the shooting at MIT. The next hour was followed by a bizarre carjacking.
Authorities wondered: Were the two linked?
The carjacking victim had left his cell phone in the SUV, and police were using it to monitor the vehicle's every movement. It was now shortly after 12:30 a.m. Friday.
Many Watertown police officers had ended their shift at midnight and were headed home when they heard a possible suspect in the MIT shooting was in their vicinity.
"All they knew at the time was this was related to the MIT murder over there," Watertown Police Chief Edward Deveau told CNN.
Officer Joe Reynolds was the first to spot the stolen vehicle, driving in tandem with a Honda Civic. He notified the station that he had the suspects in sight.
"OK, do not try to pull their vehicle over until we get you some more backup," he was told.
Officer Reynolds continued to follow them. At least seven officers soon arrived.
On Laurel Street, a side road in the middle of a neighborhood, the two brothers stopped their vehicles and immediately started shooting. "They took the gunfight to us," Deveau recalled.
Officer Reynolds kicked his cruiser in reverse to try to distance himself from the suspects.
Andrew Kitzenberg lives in a three-story home at 62 Laurel, the location where the gun battle began. He saw two men crouched behind the SUV, opening fire on police.
One officer radioed dispatch: "They have explosives and grenades." Loud pops could be heard in the background.
"Shots fired! Shots fired!" he said.
Kitzenberg ran upstairs to his third-floor bedroom and peeked out a window, capturing the chaotic scene on his phone. At 12:55 a.m., he tweeted, "Shoot out outside my room in Watertown. 62 Laurel st."
The suspects grabbed a backpack, apparently from the Honda, pulled out a pressure-cooker bomb and placed it on the ground. An explosion rocked the neighborhood, and the brothers kept unloading on cops.
"Shoot out with 5 minutes of gun fire and pressure cooker bomb," Kitzenberg tweeted at 12:57 a.m.
He followed quickly with another tweet at 1 a.m.: "PD claiming IED's on the street. Everyone stay off of laurel st."
"I actually saw them light the bomb and I saw a spark from it. As soon as I saw that spark I hit the ground," he recalled.
Up to that point, Kitzenberg believed he was looking at an intense gun battle related to the MIT killing. "When they started using explosives, then I knew it was something much more significant and pretty much knew who I was looking at," he told CNN.
At one point, one of the police officers shifted his cruiser into gear as a diversionary tactic, and it rolled toward the two shooters. They fired round after round, blowing out the Ford SUV's back window and side window.
"I hope the chief's not mad at me. The cruiser's a little bit damaged," the cop told his captain.
The officer took up a position on the side and fired at Tamerlan and Dzhokhar.
The brothers tossed out five pipe bombs; two or three exploded.
After the final blast, a shroud of smoke covered the street and an armed Tamerlan ran toward police, shooting as he approached.
"He starts closing in on one of my officers, and they're literally about 10 feet away from each other, exchanging gunfire," Chief Deveau said. "Then, he runs out of ammunition."
Neighbor Kitzenberg gave a similar account: "He was running down the street, still engaging in gunfire. ... As he got closer to the officers, he was taken down."
An officer tackled the suspect. Two others joined in and tried to handcuff him.
All of a sudden, the black SUV roared down the street. "Get outta the way," an officer screamed. Police leaped to the side at the last second.
The younger brother slammed into Tamerlan, dragging him about 20 yards. "Ran over his brother," said Deveau.
A typical gunfight lasts about a minute, Deveau said. The one with the Tsnarnaev brothers lasted about 10 minutes, with more than 200 rounds fired and three bomb blasts.
A transit officer was badly wounded in the exchange. The Watertown police on scene immediately turned their attention to trying to save his life.
The black SUV with Dzhokhar behind the wheel managed to escape, with cops giving chase.
It was shortly past 1 in the morning.
A boat leads to the big break
Blood was found inside the Mercedes ditched on Spruce Street. More blood was discovered outside the SUV, an indication Dzhokhar was wounded.
That morning, authorities took the unprecedented measure of telling residents of greater Boston to stay indoors. Schools were closed. Restaurants shut for the day. One of the nation's largest cities became a ghost town, its streets clear of people and traffic.
In Watertown, the Massachusetts State Police, FBI, and local police conducted a door-to-door search of homes on about 20 streets. They came up empty handed.
By 6 p.m., authorities said they believed the suspect was still in the region but they lifted the order to stay inside.
After being cooped up all day, David Henneberry wanted to check on his boat -- his favorite toy, his "baby" -- named Slip Away II. He had noticed from his house that its cover had come slightly off.
It had irked him for much of the day. The winds had been unusually strong that day. Henneberry figured the winds had loosened the cover.
He climbed three steps up a ladder and saw "a good amount of blood," Henneberry told CNN-affiliate WCVB.
"I said, 'Wow, did I cut myself last time?'"
"Then, I just look over there, and there is more blood," he told WCVB. "I looked back and forth a couple of times and my eyes went to the engine block and there was a body. ..."
"He was just laying there by the engine block and the floor. I couldn't see his face. I'm glad I didn't see his face," he said. "He didn't move."
Henneberry called 911.
Moments later, hundreds of authorities, ranging from FBI agents, SWAT team members and specialty tactical units, arrived at 67 Franklin Street. Gunfire and flash bangs, meant to stun people, echoed through the neighborhood.
A state police helicopter used a thermal imaging camera to determine that Dzhokhar was alive and moving. A robotic arm was used to remove part of the tarp and further reveal the suspect.
Eventually, he stood up and lifted his shirt for officers to show that he didn't have an explosive vest. "At that point," Deveau said, "we felt comfortable enough to send some officer tactical equipment to grab him and pull him away from the boat."
At 8:45 p.m., Boston police tweeted: "CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody."
About that time, raucous cheers roared down Franklin Street. Federal agents with sub-machine guns, firefighters in protective gear, SWAT team members in full body armor, hundreds of them, raise their arms in victory and hooted in jubilant fashion.
Residents on the lawn of the Church of the Good Shepherd joined in the revelry. Every time a tactical team member emerged, neighbors applauded and shouted "Thank you!"
One policeman, about 6 foot, 4 inches and 250 pounds, had stood guard for much of the night with two comrades, a formidable barricade to keep reporters away. Amid the celebratory cheers, a reporter asked if the suspect had been captured.
A smile spread across his face. "Yes," he said.
CNN's Jake Tapper, Drew Griffin and Deborah Feyerick contributed to this story.