How George Floyd Was Deliberately Murdered in Cold Blood while in Police Custody

We know that Dirty, Psychopath Killer cops do this all the time, all across the country. I have many videos.
Here is the question we, the citizens MUST answer.
Obviously, We, the People, must video the police committing these heinous abhorrent criminal acts, BUT we MUST also Stop these bastards from Murdering citizens.
If we see armed police murdering a citizen, How do we stop them?
Video what is happening, Shout at the officers telling them to stop, Tell them it is all being recorded. Call 911 for Police and Ambulance and tell them that a citizen is being murdered by other police officers.
Then what? How do we physically intervene? Charge in and drag the policeman off the person he is killing? I guess we risk being shot ourselves, BUT folks, No decent, honest Human Being can just stand by and watch these fuckers murder a citizen.
Anyone know what the law is regarding protecting ourselves and others against criminal police.
Let me know.
I hope these four officers are charged and convicted of Ist Degree Murder. I hope they get the Death Penalty. That would send a message to the other scum out there.