No we don't know that.
Correction: we know that he had traces of marijuana in his system.
Do you know what else we know?
We know that he was kicked out of school.
We know that he perpetrated vandalism.
We know that he had a history of violence.
We know that he yearned to be a gangster.
Does that mean that he should have been killed? Certainly NOT.
But he certainly was not the perfect soul that the liberal media had at first made him out to be.