I knew somebody would invoke 8th amendment, well at least we have some logical point to argue about.

The party suing the police department will definitely refer to 8th amendment. It is also possible that compensation will be awarded, the cop might also be reprimanded (if he is not already). But that will not prevent this kind of incident which was my question at the first place.

Why not, you might ask. Well, how do you enforce it? Tell cops not to use cruel and unusual punishment? How do you define cruel/unusual punishment. Think about it, if the Indian man was a criminal, or a mentally disabled person, reaching out for a gun in his pocket- what would a cop do in that case? Worry about the definition of "cruel and unusual" punishment or protect his life by subduing the suspect? How can the cop tell a difference between a mentally disabled person and a person who they just met and who was reported as "suspicious" by neighbors?

I still don't support what the cop did, but to argue that he did wrong I have to come up with a clear violation of a policy and I can't point to it. It's not as easy and clear cut as some of us think here.