> It's used as a treatment for drug overdoses ("excited delerium") which appears to be why it was used here.

Why does it “appear” that way?

Please edit your post rather than spreading misinformation.

Those on the scene certainly thought this was the case, which is basically the only reason they use that drug in the first place in the context of an arrest. I don't claim to know one way or another whether they were right, but I would note that dying of a heart attack is inconsistent with ketamine as the cause.

Maybe they gave him too much, but the article leaves one to conclude that this was somehow related to his death even though it never actually says so.