Dzhokhar Tsarnaev, the surviving suspect of the Boston Marathon bombing, has been indicted on 30 charges by a grand jury - 17 of which carry life in prison or the death penalty.
The 19-year-old was indicted on charges including using a weapon of mass destruction and bombing a place of public use, resulting in death.
Three people were killed and more than 260 injured in twin explosions near the finish line of the marathon on April 15. The charges also cover the death of police officer Sean Collier, whom prosecutors say was fatally shot by Tsarnaev and his brother a few days later.
Mr Tsarnaev's older brother, Tamerlan Tsarnaev, was killed following a shootout with police on April 19.
Dzhokhar Tsarnaev was captured later the same day hiding in a boat in a backyard in Watertown, close to Boston. According to the indictment, he had written a message on the inside of the boat that said: "The US government is killing our innocent civilians," ''I can't stand to see such evil go unpunished" and "We Muslims are one body, you hurt one you hurt us all."
Authorities said each brother had placed a rucksack containing a shrapnel-packed pressure cooker bomb near the marathon finish line. The bombs went off within seconds of one another.
"Tamerlan Tsarnaev's justice will be in the next world, but for his brother, accountability will begin right here in the district of Massachusetts," Suffolk district attorney Daniel Conley, whose jurisdiction includes Boston, said at a news conference with federal prosecutors.
Although the brothers originally came from Chechnya, the the indictment made no mention of any larger conspiracy beyond the brothers and no reference to any direct overseas contact with extremists. Instead, it suggests the internet played an important role in their radicalisation.
Before the attack, according to the indictment, Dzhokhar Tsarnaev downloaded the summer 2010 issue of Inspire, an online English-language magazine published by al-Qa'ida. The issue detailed how to make bombs from pressure cookers, explosive powder extracted from fireworks and lethal shrapnel.
The indictment says he also downloaded extremist Muslim literature, including Defence of the Muslim Lands, the First Obligation After Imam, which advocates "violence designed to terrorise the perceived enemies of Islam".
Another tract downloaded includes a foreword by Anwar al-Awlaki, who was linked to al-Qa'ida and was killed in a drone strike in 2011.
The attorney general, Eric Holder, will decide whether Mr Tsarnaev should face the death penalty. He will be formally charged on July 10.