We had a heat wave in Kansas City last week and I saw how more people were getting more easily angry. The heat wave tempers in the movie were only one of the things, but the last straw, which causes Michael Douglas' "D-Fens" to completely snap. Other people around him are also highly on edge instigating him like those Hispanic gangsters, a psychotic army store guy who freaks on him with a gun just because he wouldn't go along with his fascist sadistic gloating. Some may argue if Douglas' reactions to both those encounters were acts of self defense. But someone on the right side of the law would've called the police immediately after and officially state to them how it was in self defense. And of course, Douglas completely exits the realms of sanity with many of his other actions like holding up a fast food place with a gun with rounds of ammo for not serving breakfast, smashing up a store with a baseball bat for prices being too high, shooting up a phone booth, and breaking into someone's backyard and invading a family's private BBQ after shooting an old man's golf cart (that family was curiously mellow considering what he did, and compared to many others he ran across). There are also the numerous past allegations his ex wife have made, putting a restraining order on him, and him deliberately threatening to and breaking it. Yes, he lost his job, yes, his wife divorced him (and he apparently understandably deserved it), yes, he ran accross other jerk*** instigators during a heat wave. But, (like earlier mentioned) we all do, and most of us know our limits not to cross. Douglas didn't. And like Prentigast said, they mistreat everyone including the fish, and it doesn't give him any special right to do all the crazy*** things he did.
I am curious where Douglas slept at night and where he went during the day for the previous month up to that point, since they were saying that he lost his job a month earlier, he hadn't been to his mother's house, and hadn't been allowed at his ex's. Had he been homeless for a month, sleeping in his car? Another reason why he ended up snapping. Still no excuse though for him to do what he did