Federal prosecutors charged the surviving suspect in the Boston Marathon bombings with terrorism on Monday, outlining a chilling plot in which the man and his brother allegedly used low-grade but deadly explosives timed to detonate a block apart.

As he lay seriously injured in a Boston area hospital, Dzhokhar Tsarnaev, 19, was charged with using a weapon of mass destruction and malicious destruction of property, counts that could bring him the death penalty. He made his first court appearance in an unusual, non-public proceeding in which a federal judge and several lawyers went to his hospital bed.

The toll from the bombings, according to court documents and interviews on Monday, could have been far higher. Tsarnaev and his brother, Tamerlan, 26, who was killed Friday after a firefight with police, had a homemade arsenal of explosives. Some law enforcement officials said they think the brothers were planning more attacks.

The pair also apparently had no escape plan. The FBI found in Dzhokhar Tsarnaev’s college dorm room what appeared to be the same black jacket and white hat he wore on the day of the attack, court documents said.