Hettinger escaped the killer (sans weapon) but was “shunned by colleagues.” Why?
IIRC because he gave up his gun.
Because of multiple trials, he had to testify several times, years apart, and some of the testimony took place at the scene of the crime.
At the time this movie was made, there was a simple credo in law enforcement. You never give up your gun. They might kill you, but you never give up your gun. Hettinger gave up his gun.
In the Caine Mutiny, there's a passage where Tom Keefer, who takes over as the skipper of the Caine jumps overboard because he thinks the ship is sinking after being hit by a kamikaze. Willie Keith and some of the crew extinguish the fire and rescue Keefer. Keefer talks to Willie about the one moment in your life where you're faced with a choice, and you don't have time to consider and you make that choice in an instant, and for the rest of your life you know whether you're a brave man or a coward.
We don't think like that much, anymore, so it's difficult to understand the feelings of Hettinger and the other LAPD after the incident. Today, if you survive, you did the right thing. Then, there were things more important than your life.