NEW YORK - Bleeding and hunted by police, Dzhokhar Tsarnaev, the prime suspect in the Boston marathon bombings, who was found hiding in a boat days after the blasts, left a handwritten message describing the attack as retribution for U.S. wars in Muslim countries, CBS News reported on Thursday.

The report, citing anonymous sources, said that Tsarnaev used a pen to write the message on an interior wall of the boat, where police found him four days after the April 15 bombing.

“When you attack one Muslim, you attack all Muslims,” he wrote on the side of the cabin of the boat.

Tsarnaev said the bombings, which hit the iconic Boston Marathon on April 15, were retribution for US military action in Afghanistan and Iraq, CBS reported. He said the victims of the Boston bombing were collateral damage just as many Muslims have been innocent casualties of American wars in Iraq and Afghanistan.

Tsarnaev also said that he didn’t mourn his older brother, Tamerlan, the other suspect in the case. He called his brother a martyr in paradise and said that, eventually, he’ll join him there, CBS reported.

The note is expected to be a key piece of evidence in the coming prosecution of Tsarnaev. CBS reported that the scribblings are admissible in court and demonstrate a clear motive, backing up statements Tsarnaev made to police.

Tsarnaev made some of those statements before he was read his Miranda rights, creating a legal argument his defence attorneys surely will make. But the writings in the boat, CBS reported, constitute a de-facto admission that clearly came before police arrested him.