Bodies had fallen outside the meeting room in San Bernardino, California, where a holiday party with about 80 guests had been underway when two people armed with semiautomatic rifles and pistols walked in and sprayed the crowd with scores of bullets.
Madden, a dispatch supervisor on his way to lunch, was a mile away Wednesday when the dispatchers started frantically calling for units to head to the Inland Regional Center.
He said he had trained for events like this, but the scene was still surreal. It was sensory overload.
The fire alarms were blaring. People were moaning. Others cried out for help. Bodies lay in a room with a Christmas tree and festive decorations.
Two minutes after he had arrived at the center, he had assembled a small team to go into the meeting room.
"It was unspeakable, the carnage that we were seeing, the number of people who were injured and, unfortunately, already dead, and the pure panic on the faces of those individuals that were still in need and needing to be safe," Madden told reporters Thursday.
'The moans and the wails'
The officers couldn't be sure the shooters were gone. Some witnesses described two shooters; others said there were three. Someone said one person had escaped in a dark SUV, Madden said.
They didn't know the shooters -- Syed Rizwan Farook and his wife, Tashfeen Malik -- had fled in the truck.
Madden felt bad that he couldn't stop to help the wounded.
"There were people who were obviously injured and obviously in great amounts of pain. And that was evident in the moans and the wails that we were hearing," he said.
But he was worried the 50 or so people who fled to a back hallway were now hostages. Or the shooters were still in the building somewhere. He had to confront that situation.
Backup came quickly, and they tried to evacuate the survivors. The people hiding in the hall were reluctant to move or were too much in shock.
Officers yelled at them to come forward. They stayed. They asked several more times. Finally, one person moved, and it was a rush.
Madden -- who was born in San Bernardino, grew up there and joined the police department 24 years ago -- said he felt like his town was under attack.
Authorities have said they are still not sure of the shooters' motive, but terrorism likely was part of the killers' plan.
Officials: Farook appeared to have been radicalized
Law enforcement sources said it appears Syed Farook was radicalized and the belief contributed to the shooting motivation, though other motivations like workplace grievances could also have played a role. President Barack Obama hinted as much Thursday when he said that the attackers may have had "mixed motives."
Farook was in touch with more than one terrorism subject who the FBI were already investigating, according to other law enforcement officials. But his contacts with them were scant and months old.
David Bowdich, assistant director in charge of the FBI's Los Angeles office, told reporters Thursday that Farook had traveled to Pakistan.
And two government officials said no red flags were raised when he'd gone to Saudi Arabia for several weeks in 2013 on the Hajj, the annual pilgrimage to Mecca that Muslims are required to take at least once in their lifetime. It was during this trip that he met Malik, a native of Pakistan who came to the United States in July 2014 on a "fiancée visa" and later became a lawful permanent resident.
Saudi and U.S. officials said records show Farook also was in Saudi Arabia in July 2014. He was there for nine days, a Saudi official said. A U.S. official described the 2014 trip as Farook's "last recorded" trip to the country.
Officials had previously said neither Farook nor Malik were known to the FBI or on a list of potentially radicalized people. Nor had they had any known interactions with police until Wednesday.
Yet Farook himself had talked by phone and on social media with more than one person being investigated for terrorism, law enforcement officials said.
The communications were "soft connections" in that they weren't frequent, one law enforcement official said. It had been a few months since Farook's last back-and-forth with these people, who officials said were not considered high priority.
FBI official: 'What is the motivation for this?'
As to what role those communications played in the San Bernardino carnage, the official said, "We don't know yet what they mean."
Added Bowdich, from the FBI: "That is the big question for us: What is the motivation for this?"
San Bernardino Police Chief Jarrod Burguan echoed that sentiment, while adding that whatever led the two to launch Wednesday's assault, they could have killed more had they survived. He pointed to the discovery of hundreds of rounds of ammunition in their rented black SUV as well as in their apartment.
Authorities also found 12 pipe bombs there, as well as hundreds of tools that "could be used to construct IEDs or pipe bombs," the chief said.
"If you look at the amount of obvious preplanning that went in, the amount of armaments (they) had, the weapons and the ammunition, there was obviously a mission here," added Bowdich. "We know that. We do not know why.
"We don't know if this was the intended target or if there was something that triggered him to do this immediately. We just don't know."
Also Thursday, law enforcement officials said two smashed cell phones were recovered from a garbage can near one of the crime scenes connected to the shooting.
And a recovered hard drive shows some signs there was an effort to tamper with it, a law enforcement official said. Other electronics have been recovered and are being examined, according to a second law enforcement official.
Victims' names released
The San Bernardino County coroner on Thursday released the names of the 14 people killed
• Robert Adams, 40
• Isaac Amanios, 60
• Bennetta Bet-Badal, 46
• Harry Bowman, 46
• Sierra Clayborn, 27
• Juan Espinoza, 50
• Aurora Godoy, 26
• Shannon Johnson, 45
• Larry Kaufman, 42
• Damian Meins, 58
• Tin Nguyen, 31
• Nicholas Thalasinos, 52
• Michael Wetzel, 37
• Yvette Velasco, 27
Chief: Shooter left party under 'angry' circumstances
The nightmare began at Wednesday's holiday party, which San Bernardino's police chief said that Farook had left abruptly "under circumstances that were described as angry."
He and his wife returned around 11 a.m. (2 p.m. ET) dressed in "black ... tactical gear" and heavily armed. Then they opened fire, unloading 65 to 75 rounds.
Farook and his wife slipped out a door and into a SUV, which they'd rented locally and had Utah plates.
After officers arrived, they began chasing a number of leads. One of them led them to Farook, after another person at the party at Inland Regional Center expressed "some concern over his behavior," Burguan said Thursday.
Officers went with a search warrant to the couple's rented apartment in the neighboring city of Redlands, where they saw a black SUV drive by them, slowly at first, before speeding away.
A police car took up pursuit, and the SUV raced back toward San Bernardino. Then came shots from that vehicle, and a barrage of police gunfire in return.
The couple ended firing at least 76 rounds, while the 21 responding police officers unleashed about 380 rounds of their own, according to Burguan.
By the time the last shot rang out, the SUV was riddled with bullet holes. And Farook and Malik were inside, dead.
Guns and explosives discovered
The husband and wife didn't leave a note to explain their attack, nor did they say anything during the bloodbath, said San Bernardino's police chief.
But they left behind plenty of ammunition and explosives, including three rudimentary devices packed with black powder and rigged to a remote-controlled toy car at the shooting site. None of these went off. The remote was found inside the SUV along with another pipe-like device, which was not an explosive, Burguan said.
Hundreds of unspent rounds were discovered in the vehicle, plus two .223-caliber rifles and two pistols. All were legally purchased three to four years ago, according to Burguan.
More ammunition and more bombs were found inside the couple's rented apartment in Redlands.
Farook and Malik had enough firepower to do more killing.
"They were equipped," the San Bernardino police chief said. "... And they could have done another attack."
Brother-in-law 'in shock'
Farook, an American citizen, was an environmental health specialist with the San Bernardino County health department, which was holding the holiday party. He had worked there for five years.
In an online profile, he described himself as a "Muslim Male living in USA/California/riverside" and his family as "religious but modern."
He "enjoys working on vintage and modern cars, reads religious books, enjoys eating out sometimes. Enjoys travelling and just hanging out in the back yard doing target practice with his younger sister and friends," his profile read.
Farhan Khan said he last talked to Farook, his brother-in-law, a week ago. Farook's family -- including his mother, with whom he and his wife had left their 6-month-old daughter and claimed they were heading to a doctor's appointment -- had tried to reach him all day Wednesday but could not.
"I have no idea why he would he do something like this. I have absolutely no idea. I am in shock myself," Khan said. "I don't have words to express how sad and how devastated I am."
Obama: Mass shootings 'too easy' in U.S.
Whatever their intentions, Farook and Malik caused an avalanche of pain. San Bernardino Mayor Carey Davis saw this suffering in the eyes of relatives of those killed, whose bodies were still in the Inland Regional Center early Thursday, according to county sheriff's spokesman Deon Filer.
Davis told CNN, "The desperation and despair that they feel, we feel that for them also."
At least 10 people were still hospitalized Thursday, split evenly between Arrowhead Regional Medical Center and Loma Linda University Medical Center. The Loma Linda hospital CEO, Kerry Heinrich, said two of the victims there were in critical condition.
Once again after a mass shooting, Obama appealed Thursday for something to be done to prevent more heartache.
"Right now, it's too easy," he said. "We're going to have to search ourselves as a society ... to take basic steps that would make it harder -- not impossible, but harder -- to let individuals get access to weapons."