Identifying an Anime: Mentally Ill Boy and Murder Plot

[Archivist8405]

hello people, i'm not sure if this is the right place to post this but anyway, 
I'm trying to remember an anime that I think was a series. The only thing I remember is a specific scene:

There were some people in a car (I think it was a passenger van or a kei passenger van, but I'm not sure), including a boy who was mentally unstable (probably a serial killer?). I think he had killed his parents. He had dark hair (probably black), was wearing a black hoodie, and had a knife (or maybe a box cutter). he was short and possibly a teen. The people in the car, including the boy, were not good people they were likely antagonists. oh, and i think one of the people who he was on the protagonist's side made some shady deal with them

As they were talking, one of the men in the car said something like, "We wanted to put him to good use," or something similar. He might have also explained the boy’s backstory to the others in the car. It seemed like they were planning to assassinate an important person. I don’t remember exactly who the target was, but I think he was some sort of politician or sheriff or a police chief or something.

The boy was a side (maybe minor) character. At some point, the group decided that he should be the one to carry out the assassination. He then got out of the car. Meanwhile, the important person was giving a speech on the street to some reporters, and i think it was being broadcast live on TV. 

The boy ran straight at him, stabbed him with the knife or box cutter, pushed him, and then ran away. It all happened very quickly he just ran up, stabbed the man, pushed him aside, and escaped. Later, he got back into the car with the other antagonists. 

the art style of the anime is modern but i'm not sure if it was in 3d too or not.
I also don't know if it was a series or a movie like.
i'm sure that it's not Death Note, Phantom: Requiem for the Phantom, Zankyou no Terror or Dead Dead Demons Dededede Destruction.