2nd- What was wrong with this guy? People in the building complain so you put your dog down? Move you moron. And then to commit suicide over it? Holy crap I can't even fathom that one, grief is understandable but suicide?
I suspect there is more to it.
The dog incident might be the straw that broke the camel's back, but typically people choose to end their lives because they have no internal resources to draw upon in times of trouble, and no external resources or support systems to fall back on.
Either way, it's very sad.