thanks for sharing! (i had totally forgotten about this thread
)

I'm not and have never been involved with LAPD in any capacity. I'm only relaying what I've gathered from a couple of different websites. I can neither confirm nor deny the accuracy of the explanation below, but it seemed to be verified from one site to another.
"KMA" is used to end a radio conversation in the same manner that "Out" is in the military. To clarify, that is the final transmission. In the military, "Over" is used to indicate you are done speaking for now, but not ending the conversation.
It began when the FCC assigned the call sign KMA367 to all mobile frequencies on the VHF band. When an officer was done transmitting, he would end the call with KMA367. As time went on it was shortened to just KMA.
In 1982 LAPD switched to the UHF band and got the new call sign KJC625. It would be proper radio procedure to end a call with that, or just KJC. Apparently tradition has held on in the department and KMA is still commonly used.

No, not in that context. The K is Kicked, not kissed. Meaning, he was done and out of the fight. No longer an effective responder due to his extensive injury. This is significant in his case, because that leaves only is partner (a rookie trainee) to confront the ongoing aggressor. We saw the result.
Life is tough, but it's tougher when you're stupid.

Actually KMA in this movie means "I'm finished transmitting",
when officer Brian ended the call to report about the suspect putting a knife in Van Houser's right eye
.

thank you!

RA = Rescue Ambulance
POI = Person of Interest
KMA - Kiss My A$$

I see. You really should check it out, though! It's friggin' awesome!

i might.
i have commitment issues and find it really hard to watch serialised stuff

Actually, I'm Norwegian, so I don't know. I just watch alot of American cop shows/movies, so I've picked up on a few things. And I've heard them refer to an ambulance as an RA unit on several of these.
By the way, if you liked this movie, you should check out a series called Southland. It's very similar in style as this movie except for the "found footage" style. It's very raw/gritty and realistic.

thanks!
sorry if i poke you a bit about this, is RA then a common abbreviation in american english? i live in england and have never heard it. or is it simply police language?

RA is ambulance, as you thought. POI is person of interest.
The last one, I don't know.