Captured bombing suspect Dzhokhar Tsarnaev apparently scribbled a note inside the hull of the boat in which he was found after a historic city-wide manhunt detailing his motive for the attack. He and his late brother Tamerlan Tsarnaev placed two explosive devices into the crowd at the Boston Marathon on April 15th in retaliation for Muslims killed in Iraq and Afghanistan by US forces. “When you attack one Muslim, you attack all Muslims,” the note explained.

His note claimed that the victims of the attack — three dead and over 260 injured — were nothing more than “collateral damage” in the revenge plot.

The 19-year-old college student referred to his brother, who was killed in a police shootout several days earlier, writing that he would not mourn his loss because Tamerlan was now a martyr in paradise.

The note is expected to be a key piece of evidence in Tsarnaev’s prosecution. According to CBS, the scrawl constitutes a de facto admission that will be admissible in court because it clearly came before police arrested the suspect.