(CNN) -- Plenty of new information emerged this week about the investigation into the Boston Marathon bombings, including details of a different plot and the arrests of three more suspects. While many questions remain, here's what we learned from official statements or conversations between law enforcement authorities and CNN reporters this past week:
The Boston Marathon was not the original target, one of the brothers suspected in the bombings told investigators. Dzhokhar Tsarnaev and his brother, Tamerlan, initially considered a suicide attack on Boston's massive Independence Day celebration, which draws about 500,000 people.
The brothers chose the Boston Marathon only a day or two before the event once their bombs were ready sooner than expected, a U.S. law enforcement official regularly briefed on the investigation said.
It was also revealed this week that the bombs were built in the apartment where Tamerlan Tsarnaev lived with his wife and child, Dzhokhar Tsarnaev told investigators, according to that law enforcement official.
Three of Dzhokhar Tsarnaev's friends on Wednesday were charged in connection with the bombing: two for allegedly conspiring to discard potentially incriminating items from Tsarnaev's dorm room, and a third for making false statements to investigators.
Dias Kadyrbayev saw the pictures of the suspects released by the FBI and texted Dzhokhar Tsarnaev to tell him "he looked like the suspect on television," according to an affidavit filed in the case. Tsarnaev texted back "lol" and added, "come to my room and take whatever you want."
Kadyrbayev and Azamat Tazhayakov and Robel Phillipos went to his room and removed items, the document states.
A lawyer for Kadyrbayev told CNN that his client turned over a laptop belonging to Dzhokhar to police.
All began attending the University of Massachusetts Dartmouth in 2011, along with Tsarnaev.
The surviving suspect in the bombing is now at a prison hospital, where he is able to speak and interact with the staff, a prison spokesman revealed this week.
His condition has improved, compared to when he arrived at a Boston hospital after a standoff with police.
A source told CNN this week that Dzhokhar Tsarnaev was semi-conscious, wrapped in field gauze and "covered in blood" when he arrived at Beth Israel Hospital.
Tsarnaev appeared to have lost a great deal of blood and was making no sound until he reached the Red Zone Trauma Area, where he began to moan in considerable pain, said the source, a senior employee at the hospital. He didn't seem to utter any words, the source said.
Tsarnaev's defense team now includes Judy Clarke, one of the nation's foremost experts on keeping clients off death row.
Tamerlan Tsarnaev's body laid unclaimed until Thursday, when an extended family member arranged for a funeral home to pick up the body, the Massachusetts office of the chief medical examiner said.
Tsarnaev's cause of death will not be released until the death certificate is filed with the Boston city clerk.
On Friday, it was announced that his funeral will be held in Worcester, Massachusetts.
This decision apparently came after his parents in Dagestan said they would not bring his body back to Russia. They said through a spokeswoman that they will not bury Tsarnaev until an "independent" autopsy is conducted.
According to what the younger brother has told investigators, Tamerlan Tsarnaev was the mastermind behind the attack.
Federal agents are also looking into possible links between Tsarnaev and a Canadian boxer-turned-jihadist killed by Russian troops in 2012, a source being briefed on the investigation said. William Plotnikov and six others died in a firefight with Russian forces in Dagestan in July 2012, while Tsarnaev was visiting the region, the source said.
Katherine Russell, Tamerlan Tsarnaev's widow, remained largely out of view this week inside her parents' home. It remains unclear what, if anything, what she might have known or suspected.
According to her attorney, Amato DeLuca, the 24-year-old widow knew nothing of plans to bomb the race, and reports of her husband's involvement came as an "absolute shock" to Russell and her family.
But two sources familiar with the investigation told CNN that she spoke to her husband after his picture appeared on national television as a suspect.
The nature of the conversation remains under investigation, but the sources said there was some concern that Russell spoke with her husband but did not call authorities who were still seeking to identify the men in the photos.
The driver who was held hostage by the Tsarnaev brothers for 90 minutes before police caught up with them, spoke to CNN this week.
The man, who CNN is describing only as Danny because of privacy and safety concerns, said there was a difference of personalities between the brothers.
Tamerlan Tsarnaev kept talking throughout the ordeal, barking out orders, detailing his hatred of Americans and asking Danny to remain calm.
"If you cooperate, I won't kill you," said Tamerlan Tsarnaev, according to Danny.
While the talkative Tamerlan was the ringleader during the carjacking, the quiet Dzhokhar responded to multiple orders, such as getting money from an ATM, he said.
An uncle of the brothers claimed that a man known as "Misha" was responsible for radicalizing Tamerlan Tsarnaev. On Monday, a U.S. government official told CNN that FBI agents had interviewed Misha.
The man, whose real name is Mikhail Allakhverdov, denied ever encouraging a violent take on Islam and says he was not Tamerlan's teacher, according to a New York Review of Books writer who says he interviewed Misha.
Of the scores of people injured in the blasts, 17 remain in five Boston-area hospitals, though none is in critical condition, according to information the hospitals provided to CNN.
Bombing survivor Jarrod Clowery told a news conference how impressed he was by the first responders who helped him and so many others and how coordinated they were -- even better than the best drive by New England Patriots quarterback Tom Brady.
"No disrespect to Tom Brady, I love him, but he can't hold a candle to [those] people," he said.
One of the biggest questions is whether federal intelligence officials could have done more to prevent the attacks.
"Based on what I can see so far, the FBI performed its duties. The Department of Homeland Security did what it was supposed to be doing," President Barack Obama said this week. "But this is hard stuff."
An independent review by the Intelligence Community inspector general is under way.
James Clapper, the director of national intelligence, believes that all of the agencies involved in collecting and sharing information about Tamerlan Tsarnaev "took all the appropriate steps," Clapper spokesman Shawn Turner said.