I think the adjective you are looking for is "sufficient" reason.
I think it was!!!!!
Clearly it was sufficient. That is not up for debate, is it?
IMO the debate isn't whether the Cop was justified and/or had sufficient reason. The question is would you have killed him or not and if so why, and if not why. I probably would not have fired my weapon at all against this unarmed dude. When he cursed at me, knowing that I've got backup coming "seconds" away. I would have just hung back in my vehicle take some pictures of the guy strolling merrily down the street. Why start a chase against "two" guys when you have backup coming? See if it looks like he's armed. I'm not gonna let some big dude reach into my window I'd probably roll the window up. Epic foolhardy to try to open your door from a seated position with a big dude on the other side of the door and your window open.. WTH?
nope, it isn't. I don't live in a vacuum, I live in a world where my actions have ramifications. I supposed you don't live there. If I rush a cop because I feel like it, all bets are off on what might happen. Same is true if it is a thief who has a gun pointed at my chest. Any move I make has ramifications. The difference, the cop has justification entitled by his employment. The thief, no.
Ayup the cops are entitled and justified to be jury, judge, and executioner. It's all legal like.
Would shooting the suspect been any MORE justified if there were 3 cops standing around? Perhaps we need to start hiring lawyers to do ride alongs so they can advise the police in every potentially violent situation. You know, "Okay, now you may advise the suspect that if he attempts to take your weapon, you will tell his mother, and she will be mad", "Okay, that didn't work, now he's charging at you. Protocol states that you may make a scary frowny face at him". Would that help?
And yes, a cop is fully justified in shooting a person who is assaulting the cop and attempting to take his weapon. That's why the smart thing to do when an armed cop tells you to do the chicken dance is to do the chicken dance. Let a lawyer engineer a big payday for you. Better than ending up in the morgue. Even better, don't do anything stupid that will attract the cop's negative attention to you in the first place.