IMO This is an even more naive (and dare I say intentionally malicious) bad-faith misinterpretation of the facts.
His death had nothing to do with the Constitution, it was because of a trigger-happy, confused cop who had his back to the guy, then noticed a gun next to him (that another officer previously put there). The US government had no part in that situation at all.
The US government is responsible for the training of its agents. It is culpable as well.
That's kind of the point.
The constitution is just some rules people wrote up generations ago. It's not a magic spell that has power by itself, it is only effective as a social contract as long as power structures agree to follow it.
If armed government enforcers break it with impunity, what good is it?
If you can't exercise your rights without being murdered by a state sanctioned thug, then it's not really a right. Also, has he been indicted yet? charged?
I think that's exactly the point. The constitution didn't prevent his death.
What are cops if they're not the government? Are they private corporations?