Why did that guy on the roof want to kill himself?
What do you think caused him to attempt suicide before Riggs came onto him and rescued him by jumping onto a safety mat with him from that roof? (Also, wasn't the scene a little like that similar part in Dirty Harry (1971)?)
Maybe he had a misfortune in the relationship with someone? People bullied or insulted him? He's had enough of the world? Or what could it have been?