Is this story true or an Urban Legend I need to know?

The story focused on a random stranger passing by, and this nerd. (This guy apparently looked like your stereotypical nerd; thin, weak physique, glasses, no facial hair, intellect) anyway, this nerd was a mild Schitzophrenic, and believed the other man was going to kill him. The adrenaline kicked in; he wrestled the other person down to the ground, overpowering him, sat on his chest and wrapped his thighs tightly around the other man's throat, squeezing him to death. He was later arrested for murder. I have heard the same snippets of the story from 3 other people, all of which contained the same theme of the nerdy guy suddenly 'snapping' and killing a random person in that manner. There were no other known reasons why this man did what he did. This was also apparently on the news. But I'm not sure if it is true or not. If anyone could give me some input/reasons on this I'd appreciate it, I can't find the story on Google, either.