Apparently this guy finally cracked. After at least a couple decades of teaching (I'm basing this assumption on his salary), he got sick of the administration, barricaded himself in a classroom, and said he'd planted a bomb. They evacuated the entire building and police rushed in to talk with him. Eventually he admitted there was no bomb and he surrendered.
When I started reading the article -- "A Bronx educational building that houses three public middle schools with about 1,200 students was evacuated by the authorities around 8:30 a.m. Friday after a disgruntled teacher claimed to have planted a bomb in the library" -- I thought it was going to be my former school.
The fact that the school building has been split into three schools means that the school was not doing well, got shut down, and the Region replaced it with three new ones. Which means it was probably not a pleasant place to work. He'd also recently been charged with corporal punishment -- not something one resorts to in an orderly setting.
Now, it's entirely possible that this guy had serious issues outside of teaching in a challenging school -- but trying to teach in a place like that for 20+ years can't have helped.