The latest piece of evidence in the Boston Marathon bombing case: A confessional note found in the boat that bombing suspect Dzhokhar Tsarnaev was hiding in when police caught him.

According to CBS News, Tsarnaev wrote that the bombings were a response to U.S. military action in Afghanistan and Iraq. He added that he wasn't sorry that his brother Tamerlan had died because he was now a martyr in heaven and that Tsarnaev planned to join him.

CBS News didn't publish the full text of the note, save for this one phrase: "When you attack one Muslim, you attack all Muslims."

The note, which sources say was written in pen by Tsarnaev as he lay bleeding in a boat in a backyard in Watertown, Mass., was also shared with NBC News.

The picture of Dzhokhar Tsarnaev that emerged after the bombings was one of a good and popular student who was voted captain of his wrestling team. Now, this note might help counter the narrative that Tamerlan was a religious extremist who convinced his relatively sociable teenage brother into allegedly setting off bombs near the finish line of the Boston Marathon.

There were signs when Dzhokhar entered college that he was becoming disillusioned with his life in the United States. His grades begin to fall at UMass Dartmouth. His classmate, Sanjaya Lamichhane, told The New York Times that Tsarnaev once told him: "God is all that matters. It doesn't matter about school and engineering."

That was about the same time that Tsarnaev began tweeting things like this:

Sources told CBS News correspondent John Miller that the note would be admissible in the upcoming trial. Tsarnaev is set to appear in court on May 30.