there are plenty of reason why a person wouldnt...
- cant swim
- they are afraid
- they are indifferent
- they feel its too dangerous
- they panicked
...some of those are valid reasons...some a little less so...but generally, your average person is not jumping in a freezing lake to save someone they dont know...that officer could have sat there and just called the FD to come deal with it, and probably not suffered any real repercussions...i dont know her job description, but im going to guess that water rescue isnt in it.
but the first thing they teach you in any emergency response course is rarely is anyone going to act first...everyone is going to stand around until someone tells them what to do...
thats why you dont say
"someone call 911" you say
"you, in the blue shirt, call 911"....."you, in the red jacket, get the med kit"....
and never assume what YOU would do, is what your average person is going to do.