The US Government is killing our innocent civilians but most of you already know that. As a [UI] I can’t stand to see such evil go unpunished, we Muslims are one body, you hurt one you hurt us all. Well at least that's how muhhammad (pbuh) wanted it to be [for]ever, the ummah is beginning to rise/[UI] has awoken the mujahideen, know you are fighting men who look into the barrel of your gun and see heaven, now how can you compete with that. We are promised victory and we will surely get it. Now I don’t like killing innocent people it is forbidden in Islam but due to said [UI] it is allowed. All credit goes [UI].
Stop killing our innocent people and we will stop.
The Government's full response is here.
What conclusions does it draw from the note?
This writing, which bears hallmarks of al-Q’aeda-inspired rhetoric, suggested that Tsarnaev might have received instruction from a terrorist group. In addition, the fact that Tsarnaev used the word “we” (i.e. “We are promised victory and we shall surely get it. . . . Stop killing our innocent people and we will stop.) suggested that others might be poised to commit similar attacks and that Tsarnaev was urging them on.
I think both conclusions are a stretch to say the least. There's nothing in that note to suggest he was "instructed" or received training. I think it's more plausible he is repeating what he read online at websites and watched in You Tube videos. I also don't see where he suggests others are contemplating similar attacks. He clearly says in the beginning the "we" refers to Muslims -- he doesn't restrict it to radical Islamic terrorists.
In all, I think the note provides some support for the defense theory it intends to present in mitigation during the death phase that he was young, enamored of his overpowering brother and taking direction from him. The primary goal of the defense is to save Jahar's life, not convince a jury he didn't participate in the bombing.