16 years for murder?

I just do not understand how things work with the legal system. Not too long ago a friend of mine lost her baby girl, her 2 year old daughter was murdered by her then boyfriend. He was also a policeman. Not the kind of person you would think could do such a thing, but he did. He said she just wouldn't stop crying. It was so sad, and still is.
He had his trial yesterday. He ONLY got 16 years for taking that sweet baby's life. 16. That's it. There are people that spend their whole life in prison over drugs or armed robbery, but this guy, this ex-cop, only got 16 years for KILLING a precious little girl. It turns my stomach. Seriously.
Now, maybe Im so upset over this because I knew that baby girl, but it is just disturbing to me. He also is not going to be put in with the general public, because he is a cop. I just do not understand it.
It's just not fair. Thats all.