Suspect: Boston attack was payback for hits on Muslims From Susan Candiotti, CNN May 16, 2013 -- Updated 1511 GMT (2311 HKT) Source: Dzhokhar Tsarnaev left a message in boat where he was found hiding He wrote that the Boston Marathon bombing victims were collateral damage Dzhokhar also said he expected to join his brother in death The 19-year-old is being held at a federal prison hospital (CNN) -- Boston Marathon bombing victims were collateral damage in a strike meant as payback for U.S. wars in Muslim lands, the surviving suspect wrote in a message scribbled on the boat where he was found hiding, a law enforcement source told CNN Thursday. In the message, Dzhokhar Tsarnaev also proclaimed that an attack on one Muslim is an attack on all and said he would not miss older brother Tamerlan Tsarnaev -- who died after a firefight with police three days after the bombing -- because he would soon be joining him, according to the source. The writing on the inside of the boat dovetails with what Dzhokhar, 19, told investigators questioning him in a Boston hospital room shortly after his capture, the source said. CNN has previously cited U.S. officials in reporting that Dzhokhar said U.S. involvement in Afghanistan and Iraq were motivating factors behind the April 15 attack, which killed three people and wounded 275. According to authorities, the Tsarnaev brothers fashioned explosive devices from pressure cookers and other materials and detonated them near the finish line of the race. Three days later, authorities released their images to the public as suspects in the case. Investigators believe they then killed MIT police Officer Sean Collier and hijacked a car before battling authorities in a wild firefight on a Watertown, Massachusetts, street. Nearly 24 hours later, police found Dzhokhar hiding in the boat after the owner called police to report someone was inside of it. The final hours that paralyzed Boston Dzhokhar -- who suffered gunshot wounds to the head, neck, legs and hands -- is being held a federal Bureau of Prisons medical facility in Devens, Massachusetts. Tamerlan was secretly buried in a rural Virginia cemetery this month following protests from Massachusetts residents and officials against burying him in that state. Of particular interest has been Tamerlan's 2012 trip to the semi-autonomous Russian republic of Dagestan, home to numerous Islamic militant groups that have warred against Moscow's rule. Russian authorities asked U.S. officials to investigate Tamerlan before the trip, saying they believed he was becoming increasingly involved with radical Islam. U.S. officials learned after the bombings that Russian officials had intercepted a 2011 phone call between the suspect's mother, living in Dagestan, and one of her sons, in which they reportedly had a vague conversation about jihad, a law enforcement official told CNN earlier. Some lawmakers, particularly Republicans, have been critical of how law enforcement, intelligence agencies and the administration of President Barack Obama handled the Russian tip. While Tamerlan and his mother were added to a terror database following the FBI investigation, Tamerlan was allowed to make his Russian trip in 2012, returning six months later. Timeline: Boston attack, aftermath CNN's Michael Pearson contributed to this report. May 3, 2013 -- Updated 0939 GMT (1739 HKT) What does Katherine Russell know?