The man was obviously desperate. He probably lost his job, and couldn't find work. This impending court date charging him with "contempt" for failing to pay child support certainly had something to do with this man's horrible choice.
The system is rigged against men. What happens if a guy can't find work? How is he supposed to pay child support?
He was probably scared he was going to lose his kids, have them turned against him by his ex-wife, etc. This kind of thinking motivates a lot of murders. "If I can't have him/her/them then no one will." with a bit of "I'll kill ____ before ___ can be corrupted" thrown in. Such motivation is not morally legitimate, but it is very human thinking which reappears all the time in various crime stories.
Note that he was divorced. This is not normal or natural. Marriages need to be a lot more permanent than they are today. Divorce is way too easy. Men and women divorce their spouse just because they're bored, want to give up when the slightest difficulties emerge, and/or move on to the next new, exciting thing (person).