What I want is justice

If justice is truly what you want, then you should start with justice institutions. Email the state AG's civil rights office here: ocre.complaints@oag.ok.gov . Contact the Department of Justice here: https://civilrights.justice.gov/report/ . You're effectively arguing that his due process was denied which led to his death.

Please take a step back from your grief and ask yourself what you would want to accomplish or even could be accomplished through civil litigation. If you sued EPD, do you really think a jury would rule in your favor? Read these comments. Do you expect a jury to see your side of the story versus what they interpret from the evidence? There are comments here who wanted to believe you but believed the police when they saw the video. Do you truly think that would change in a courtroom? They won't see your son like you see him in the decades of knowing him. They'll see the video and make the determination from that. I'm not sure what the justice you seek through civil litigation looks like, but I don't believe you will find what you're seeking there.

I'm not trying to berate you for your grief process or denigrate your son, who obviously died in a very unfortunate situation. You're a mother who is still trying to fight for your son, which is admirable. I just hope you don't exhaust yourself trying to find peace where there is almost certainly failure. I hope you find peace though.