Yeah, I was an LEO for about 15 years here in Colorado.

And understand...I agree wholeheartedly that the officer and his superiors used poor judgment in pursuing this suspect as they did. I would've shown up at the meet with the guy (in uniform and marked car) and been straight up with him. Dude...give up the keys or go to jail. Having said that, I don't know what went into the decision making process of the officer and his supervisors. Maybe (probably??) they have information on this we don't have.

My only argument is that the officer verbally identified himself to the suspect. The suspect resisted, the suspect escalated the encounter by producing a deadly weapon and the officer responded. Appropriately, in my opinion.

As to the statute you cited I think you're missing an important point. The statute specifically states:
...if the peace officer or firefighter is in uniform OR the person committing an assault upon or offense against or otherwise acting toward such peace officer or firefighter knows or reasonably should know that the victim is a peace officer or firefighter.
Based again on the totality of the circumstances I don't think it would be difficult at all to prove a case of murder if he'd killed the officer. The guy knew he'd committed a crime and now, suddenly, here's a guy claiming to be a cop saying you're under arrest for exactly the crime you know you're committing. To me, that fulfills the "reasonably should know" part of the statute.

Also, I just watched a video where witnesses stated the officer was simply trying to control/subdue Contreras and verbally identified himself as a police officer several times.