Great answer.

I'm an Australian cop, so I have an idea about the situation.
When it's high stress and you feel like the enemies are closing in around you (an experience I've felt a few times), your decision making skills deteriorate a bit and you tend to go into fight/flight/freeze mode.
Most cops will instinctively go into fight mode and shoot back, it's kind of in our nature and a reason we gravitate towards military/paramilitary jobs in the first place.
The guys were clearly in flight mode and the sensible option was missed due to stress.
I think the movie adequately displayed the errors in judgement made by experienced cops when dealing with high stress, life and death situations.
We are human at the end of the day, and hindsight is a wonderful thing. Often I look back and think of how I could have handled a situation better, but ultimately I have to own my decisions and try to justify them to the multitude of people out to condemn me
Adjust your face; take your time, because it's about to be rocked off - permanently

I don't know about a "rookie mistake". I've never served a day in my life (as a police officer) but I would be either jumping those fences in the alley, breaking into a garage, or hugging the side of the alley and taking cover behind anything I could find like my life depended on it! I agree that hanging out in the middle of the alley is a mistake for sure.
There are no problems that cannot be solved with a can of brake clean and a lighter

Tatlor did say that he messed up after getting shot.

Yeah I don't know why they just stayed in the open. And they definitely should've told that chick that if she made noise, the people outside would kill them all.
"The saddest thing in life is wasted talent." ~ A Bronx Tale (1993)

Yes. Also sitting in that ally shouting for help wasn't really the smart thing to do. And if they would have been able to shut that stupid bitch in that appartment up, they probably wouldn't even have been found.