Boston Marathon suspect Dzhokhar Tsarnaev downloaded bomb-making instructions from an al-Qa'ida magazine, legal documents have revealed.
He also gathered online material on Islamic jihad and martyrdom and later scrawled anti-American messages inside the boat where he lay wounded until his capture, a charge sheet alleged.
The 30-count indictment contains the bombing charges, punishable by the death penalty, that were brought in April against the 19-year-old Tsarnaev, including use of a weapon of mass destruction to kill.
It also contains many new charges covering the killing of a police officer and the carjacking of a motorist during the getaway that left Tsarnaev's older brother, Tamerlan, dead.
"Tamerlan Tsarnaev's justice will be in the next world, but for his brother, accountability will begin right here in Mass- achusetts," Suffolk District Attorney Daniel Conley said.
The indictment provides one of the most detailed public explanations to date of the brothers' alleged motive – Islamic extremism – and the role the internet may have played in influencing them.
Three people were killed and more than 260 wounded by the two pressure-cooker bombs that went off near the finish line of the marathon on April 15.