My cat regularly kills?

My cat kills rats, molls and mice (which I suppose is normal) But this morning I found a dead squirrel on my doorstep. It just broke my heart. Well, it breakes my heart every time he kills. But people say "Its normal" that's what cats do". But I can't get the picture of the dead squirrel out of my head. How do I get over this? What would you do?