Buried in his best suit in his home town with the same civilian ceremonials as anyone else. After all, we wouldn't want to be accused of hypocrisy in saying that one perpetrator who damages people using one type of method should be treated differently from another perpetrator who uses a different kind of method.
Do we know that Tamerlan Tsarnaev was a bad man? Only if we know for certain that his soul is in Hell. That is the only criterion for knowing whether a person is evil, as the true character of a person is only revealed after judgement. If his soul is in Purgatory, he cannot be considered to be evil because God has deemed him worthy of salvation. And since we don't know where his soul is, we don't know whether he is evil or not. Making invidious assumptions about his character without knowing all the facts about him (and the most important facts about the quality of a person are those that are revealed in the next world) is probably a calumny because everything we say about him is ... well ... being said about him. We're not talking about an abstraction but about a still-living creation that is still loved by God.
The real entity that is 'Tamerlan Tsarnaev' is no longer with us. People are only dumping on his corpse. It's said that every day, as we move our bodies in our daily lives, we dislodge billions of dead cells from our surface areas (skin, hair, etc.). We are not the dead cells we leave behind on our furniture, floors and bed linen as we move on. 'Tamerlan Tsarnaev' is not the corpse he left behind as he moved on. Dumping on his corpse is like someone trashing your school locker because they don't like you. Immature.