Accused Boston Marathon bomber Dzhokhar Tsarnaev has been charged with using a weapon of mass destruction in connection with the blasts that killed three and wounded at least 176 last week.
The charges were unsealed hours after Tsarnaev had his initial court appearance from his hospital bed, during which he indicated he understood the proceedings against him and spoke once -- saying "no" when asked if he could afford a lawyer.
The charges came after the White House decided against treating Tsarnaev as an enemy combatant.
The case being built against the 19-year-old college student includes one count of using a weapon of mass destruction resulting in death, and one count of malicious destruction of property. The Justice Department released a statement indicating that the charges could carry the death penalty or life in prison.
"Although our investigation is ongoing, today's charges bring a successful end to a tragic week for the city of Boston, and for our country," Attorney General Eric Holder said in the statement. "We will hold those who are responsible for these heinous acts accountable to the fullest extent of the law."
Dzhokhar Tsarnaev was arraigned at his hospital bed, law enforcement sources said, a session that was first reported by ABC News affiliate WCVB.
Tsarnaev nodded in the affirmative to several questions at his initial court appearance, according to a transcript of the session, acknowledging that he understood his Miranda rights and that a federal defender, William Fick, was present to represent him.
Asked, "Can you afford a lawyer?" Tsarnaev said, "No," to which the presiding judge, Marianne B. Bowler, noted, "I have provisionally appointed the federal defender."
Bowler found Tsarnaev "alert, mentally competent, and lucid. He is aware of the nature of the proceedings."
After conferring with the attorneys, the magistrate set the next court date as May 30.
Tsarnaev was awake and responding sporadically in writing to questions Sunday night. Officials were asking about any possible cell members and other unexploded bombs. There have been no additional details yet on his answers.
Tsarnaev is being treated at Beth Israel Deaconess Medical Center in Boston, where he is listed in serious but stable condition. The federal complaint states that he had wounds to the head, throat, legs and hand.
The newly filed criminal complaint lays out in far greater detail the moments leading up to the bombing attacks, and the evidence authorities amassed as they tracked the alleged killers.
The documents reveal, for instance, that the FBI searched Tsarnaev's college dorm room and found what they believe were the white baseball cap and black jacket that the accused bomber could be seen wearing during the attack.
In the minutes before the attack, authorities describe how surveillance cameras captured the two brothers as they walked up Boylston Street in the direction of the Boston Marathon finish line. At 2:41 p.m., nine minutes before the bombing, the two men can be seen standing about half a block from the finish line. Then, at 2:42 p.m., the man believed to be Tamerlan Tsarnaev breaks off from his brother and heads towards the spot where the first blast occurred.
The man believed to be Dzhokhar Tsarnaev, meanwhile, remains in view of the cameras.
"He can then be seen slipping his knapsack onto the ground," the charging document states. "A photograph taken from the opposite side of the street shows the knapsack on the ground at Bomber Two's feet."
Dzhokhar can then be seen fiddling with his cell phone, and appearing to take a photograph with it. When the first blast occurs, and crowds turn to flee, Dzhokhar "appears calm ... then calmly but rapidly begins moving west, away from the direction of the finish line. He walks away without his knapsack."
Ten seconds later, the second blast occurs.
The report also provides the first description from the man whose car was hijacked by the alleged bombers on the evening their photographs were released to the nation.
Around midnight, the man is sitting in his car when one of the accused bombers comes up and taps on the passenger side window. When the victim rolled down the window, the suspect reached in, opened the door and got in. "Did you hear about the Boston explosion?" the suspect asked. "I did that."
The suspect removed a magazine from his gun, showed the man a bullet and reinserted the magazine. He then said "I am serious."
The suspect forced the victim to drive to another location where they picked up the other suspect. They spoke in a foreign language, the complaint said. The victim escaped when the two men got out of the car at a gas station on Memorial Drive.
Today's court appearance occurred as Tsarnaev's parents have been defending their sons' innocence in interviews in Russia. The mother of the bombing suspects told ABC News she spoke to her eldest son minutes before a violent standoff with police in the streets of Watertown, Mass.
Tamerlan Tsarnaev, 26, called his mother early Friday morning, alerting her that police were following him and his younger brother and that there had been a shooting.
"'The police, they have started shooting at us, they are chasing us,'" Zubeidat Tsarnaeva told ABC News in a telephone interview.
The conversation ended when Tsarnaev said, "'Mama, I love you,'" his mother said.
Tsarnaeva got frightened and started to cry and shout. He told her Dzhokhar Tsarnaev was with him before the line cut off.
Her daughter called later to say that Tamerlan had been killed.
Last week's twin bombing killed three, including an 8-year-old boy, and wounded about 170. An MIT officer was allegedly killed by Tsarnaev and his older brother Tamerlan, and a Boston transit cop was badly wounded in a subsequent shootout.
New details emerged Sunday night about the dramatic capture after a 20-hour manhunt for Tsarnaev after he managed to escape a gunfight with police in Watertown, Mass., that killed his older brother.
As police and federal agents closed in after a Watertown resident reported there was a bloodied person hiding in his boat, a helicopter beamed back thermal images of the outline of Tsarnaev's body.
The orders went out to do everything to capture the teen alive even after an initial exchange of gunfire.
Police quickly surrounded the boat and there was a brief but ferocious volley of fire. Watertown Police Chief Edward Deveau told ABC News Sunday that negotiators demanded Tsarnaev show his hands and lift his shirt. Authorities were worried Tsarnaev was wearing a suicide vest. He was not.
"He was very slow and lethargic in every move that he made and they could see that there was no device on his chest. They kept creeping closer to him and then they felt it safe enough to pull him away from the boat," Deveau told ABC News' Martha Raddatz.
From that point, Tsarnaev was raced to Beth Israel Deaconess Medical Center, where investigators hope to get answers to questions about motive and the possibility of accomplices.
TIMELINE: From Terror to Manhunt to Capture
Nowhere were there more questions than at the University of Massachusetts Dartmouth, where Tsarniev was known as just an ordinary student.
"Literally, when I seen him he was just regular. He walked past me, we had a brief conversation and then I asked him for a ride home and he told me, 'Yeah,'" said Andrew Glasby, who lived at the same dormitory where Tsarnaev was staying after the marathon bombings.
Another friend, Zach Bettencourt, even asked Tsarnaev about the bombings.
"I talked to him in the gym about the bombing and he was like, 'Yeah man, tragedies happen all the time,'" Bettencourt said.
The night after the bombing, Tsarnaev tweeted, "I'm a stress free kind of guy."