It is a movie so they obviously took some creative licenses with procedure and emotional reactions. Plus cops probably get threats all the time so they approach every situation with the same amount of caution. You see someone running after a car chase, their first instinct is to follow not to wait for backup. With my own gun in my hand and back up on the way, I wouldn't have even thought to grab their gun.

What really bothered me was the fact after Taylor got shot, why didn't Mike drag Taylor to the truck. If not that, then he could've dragged him somewhere else instead of being in the MIDDLE of the alley. My dad also said the Cartel in America wouldn't have the balls to take a hit on the police (he's ex. ICE) so that kind of bothered me after he said that.
"Calm down, Doctor! Now's not the time for fear. That comes later"

Remember they were trying to escape and scaling walls and what not is not as easy with an assault rifle hanging around.

What bothered me most was that Pena's character provided no security after seeing Jake shot. Pena became emotional and did not cover his partner and his ass. Pena should have pulled Jake to safety and engaged into a defensive position and wait for back up.<<<
If it's any consolation, that inattention to detail was seen in their first stop of the movie, the two-door Cutlass or Monte Carlo they pursued, then stopped in a PIT maneuver, after which the driver and passenger emerged firing.
Once the shooting was over, the cops never made any effort to 'clear' the back seat. There we a couple of cuts in the dash-cam video, but the time codes showed they were just fractions of a second, and neither officer approached the vehicle and made a close inspection of the back seat area where there could have been more passengers/shooters. Gyllenhaal appears to glance at the area through the front door from several feet away, but that's it.
At least they were consistent in failing to watch their sixes.
Let's not even get into an officer walking into a house, apparently with reason enough to draw his weapon, and yet giving one hand over to carrying the hand-held camera he later uses to take a peek in the bathroom.

Yes you are right. I bothered me too. Remember Jake's character is a Marine too, so he knows how to use an assault rifle. It's not rocket science, the gang bangers were able to operate them. The magazine was already inserted, the charging handle was already was pulled, and the lever was set in full auto. Anyone could pick it up and just pull the trigger. I would say 99% of cops would know how to operate an ak. Insert magazine, pull charging handle, select fire type, line up iron sights, squeeze trigger.
What bother me was running into a building after a perp without proper back up, especially after being warned there was a hit placed on them. I would treat every traffic stop or call as a possible ambush.
What bothered me most was that Pena's character provided no security after seeing Jake shot. Pena became emotional and did not cover his partner and his ass. Pena should have pulled Jake to safety and engaged into a defensive position and wait for back up.

I agree with Jamasian. That, and they were probably so preoccupied with getting the heck out of there that they probably didn't even think about it.

Very good point.
Cult Leader my minds frightening, I drink blood from a human skull like a Viking

Did anyone tell you that Jake was ex-military? Oh yes, about 4 dozen half-wits here repeated it like they were breaking the news. So I guess we're clear on that lol.
then whoa, differences

an AK is not to be messed around with if you have no experience.

"Deadlands 2: Trapped"
http://www.imdb.com/board/11103262/

Jake Gyllenhaal's character was ex-militarythere is no way he wouldn't know how to use an AK.

the lead character was meant to be a marine. so pretty stupid move there by him.
Yeah I found a lot of this film to be stupid, frankly it seems like a feel good cop hero worshipping delusional propaganda.

Didn't know he was a marine. He sure as HELL didn't perform like one in the gun battle. I have bad vision, but I have shot a glock and it is very easy to aim. They should have hit at least ONBE gang member if they had aimed there weapons properly.
Cult Leader my minds frightening, I drink blood from a human skull like a Viking

jake gyllenhall's character was a marinethey can shoot any weapon.

Once loaded you only need "a" hand to operate "those kind of weapons".
Besides which, "JohnGaltJunior" has summed it up perfectly, no need for more discussion.

Its too bad he got shot in the hand. You need hands to operate those kinds of weapons.

Brian Taylor (Jakes character) was a former marine, I'm 100% certain he would have had training with many different AK style weapons.

Jakes character is ex soldier I doubt that he cant use it

It was mentioned in the beginning of the movie that Brian Taylor (the character played by Jake Gyllenhaal) was a former Marine. This should probably mean that he has at least basic training on the AK

He was a former Marine, assuming he spent ANY time overseas, he would know how to use an AK.

I think I would consider being out numbered, out gunned, and on the low ground, a dire need of firepower.

Jamasian_man is right on the money. you learn this in the military as well. leave weapons on the ground that you are not issued. unless ofcourse you are out of ammo and in dire need of firepower. The movie portrays it right.

It didn't bother me but here are some reasons that worked for me:

1. They didn't trust a gang weapon; in a life or death situation would you rather trust on your own familiar weapon or a strange one that might jam or whatever?
2. They didn't have any AK ammo, so assuming there's one mag in it, you would spray that thing empty in about 3 seconds
3. They didn't have the time/mind to consider the reasons above and just wanted to get the heck out of there

It's called panic.
IMDB as of late, sold out and became like City Data and about.com, worthless bureaucrats.

because cops don't use assault rifles? yeah, ok. cops may train on the regular with their semi-auto pistols, but they are trained and handle/handled a variety of weapons. be it in training or on the job.