Pro-gun American checking in... This is fucking absurd. Why people leave loaded, ready to fire handguns laying around in the open is beyond me. I keep a gun inside a safe, which is then inside my nightstand, with the slide open and magazine out for safety. There is no sense of keeping it loaded, ready to fire, unless you deal crack/meth and are expecting to get robbed. Also, in an apartment, a handgun is a huge liability. The bullets can travel through walls so easy and you don't know whats on the other side of those walls.
I hope the gun owner is charged with child endangerment, child abuse, manslaughter, every other possible thing, and the mother sues the shit out of him and his insurance company.