The contents of the note, written while Tsarnaev was hiding from police inside a boat, were entered into evidence yesterday in the U.S. District Court in Boston.
"I do not mourn because his soul is very much alive," Tsarnaev wrote in reference to his his older brother Tamerlan.
Tamerlan Tsarnaev died on his way to the hospital following a manhunt that ended in gunfire.
"God has a plan for each person," the note continues. "Mine was to hide in this boat and shed some light on our actions."
"The U.S. Government is killing our innocent civilians. I can't stand to see such evil go unpunished, we Muslims are one body, you hurt one you hurt us all ... you are fighting men who look into the barrel of your gun and see heaven, now how can you compete with that."
Newly released evidence has lead prosecutors to believe the brothers had guidance in carrying out the 2013 marathon bombings, if not directly then from digital al-Qaida propaganda.
"The Marathon bombs were constructed using improvised fuses made from Christmas lights and improvised, remote-control detonators fashioned from model car parts," court documents read. "These relatively sophisticated devices would have been difficult for the Tsarnaevs to fabricate successfully without training or assistance from others."
Dzhokar Tsarnaev stands charged with killing four people using a weapon of mass destruction. If convicted, Tsarnaev could face the death penalty.