As someone who watches too many action movies. Wouldnt the correct police response be to ask the suspect (sanchez) to put his hands behind his head and slowly go to the ground. The suspect shouldnt even need to be reaching to lift up his jacket if the cops were in control of the situation.
Seems like they were just really poorly trained and got lucky that this guys history (something they didnt know at the time) will allow them to get away with being shitty cops.
They're trying to talk to the guy and get him to calm down. They don't have control of the situation - that's what they are trying to establish. They don't have telepathic powers- the situation is only going to be stable if the other party is calm and cooperating fully, which he is not. I'm not sure why you think that if they just asked nicely for this guy to put his hands behind his head and go to the ground that he would just do so willingly.
The issue w/ that guy is that he's a felon holding onto a gun. He doesn't want to be searched because if he is, they'll find the gun on him and he's screwed. That's why he flashes them in an attempt to de-escalate the situation himself. It doesn't work, and that's when he panics and runs.
This has nothing to do with "bad training". The fact that they were called in on this guy means that this guy's in a "try to run" or "surrender" situation w/ no good options ahead of him. They are attempting to de-escalate, but it doesn't work here because of factors that are entirely out of their control. They likely can intuit that
something's up w/ him based on his behavior, but again, they're not telepathic- they don't and can't know just how bad a no-win position this call has put this guy in.
And once he runs, it escalates and ends in a matter of seconds. The cop closer to him makes contact, the gun becomes visible, and the closer cop tries and eventually succeeds in wresting it away. The cop further away starts shooting after the gun becomes visible out of fear that it (or another weapon) will be used on his partner. His partner uses the weapon that he wrested away on the man because he doesn't know where all the shots are coming from and doesn't know if all. (This happens a lot- if one person starts shooting others are often joining in because in the moment you can't distinguish the source of the sounds.) The situation devolves into chaos once the guy starts running, and looking at their actions, none of them appear to be malicious or go far beyond what's necessary in the situation, considering the context.