Bleeding and hunted by police, Dzhokhar Tsarnaev scrawled a note inside the hull of the boat where he was hiding saying that the Boston Marathon bombings were retaliation for American action against Muslims, sources told NBC News on Thursday.

In the note, Tsarnaev, the lone surviving suspect in the marathon attack, said many of the things he told investigators from his hospital bed days later, after his capture, the sources said.

The note was first reported by CBS News.

Tsarnaev was discovered hiding in the boat, in suburban Watertown, Mass., on April 19 after a daylong manhunt that paralyzed Boston and its surroundings. He had been wounded in a firefight with police.

Tsarnaev, 19, is in a federal prison hospital in Massachusetts and has been charged with using a weapon of mass destruction. He could face the death penalty. His older brother, Tamerlan, was killed in the firefight.

Three people were killed and 264 injured when two bombs exploded near the marathon finish line April 15.

Dzhokhar Tsarnaev told investigators in the days after his capture that the brothers acted alone and were defending Islam after the American-led wars in Iraq and Afghanistan, U.S. officials have told NBC News.

Investigators are also focusing on a six-month trip to Russia that Tamerlan Tsarnaev made last year, looking for clues to his radicalization. He was buried last week at a Muslim cemetery in Virginia after cemeteries in Massachusetts refused the body.