I absolutely would never leave any of the guns (that I lost when they fell from that canoe) locked in my car while parked overnight at an apartment complex. Locked in your car in your own locked garage might be ok-—but this guy was not thinking clearly when he did that, IMO.
I'm going to lay odds that the car was a department vehicle as well (2009 Impala) and as such (with Maine plates) was targeted by someone who expected to find goodies.