See? There you begin to have a point... citing the 5th amendment, one could make the argument that George Floyd was killed and, therefore, "deprived of life [...] without due process of law". Of course, one could equally argue that "A seizure or forcible restraint; an exercise of the power to deprive a person of his or her liberty; the taking or keeping of a person in custody by legal authority, especially, in response to a criminal charge." otherwise known as an "arrest" - that was the legal definition I quoted, by the way - is, in fact, due process of law. For one to be held to account for their actions, they often are literally held... in jail, awaiting trial unless they are bailed/bonded out (if applicable). Arrest is a part of the process of law.
George Floyd's death has absolutely nothing to do with the 8th amendment. Those that think it does, don't understand the Constitution, American law or the American legal system. But that's understandable... some lawyers and judges have difficulty too... that's why appeals courts exist as well as the SCOTUS.
I don't blame people for not knowing the nuances of law - there are a lot! - but I do blame people for speaking about things they know little-to-nothing about. You've learned something though. Think of how much more there is out there to know... and get started! Knowledge is power. When you convey information that is incorrect, incomplete or incompetently conveyed you make people weaker. Become powerful! In so doing, you have the ability to make those around you more powerful as well.