Montreal riots caused by what?

Journalism students at one time were taught to answer the following in any good news article: who, what, where, why, when, and how. Apparently this is no longer being taught in journalism schools or at least not taught to those who go to work for The Associated Press and The Dallas Morning News.

The Dallas Morning News reprinted an article from The Associated Press about riots which took place in Montreal, Canada. The article read riots broke out after a peaceful protest over a man who was shot by police. No where in the article did it explain why the police shot the man. One was to think the police just roam the streets shooting people at will.

Upon further exploration into the Internet, the truth was unearthed after this laborious effort. The day before the riots the police anti-gang unit was in Henri Bourassa Park, in Montreal North. The police were arresting one person when a crowd of over twenty youths menacingly surrounded the police when some lunged towards the police, causing the police to open fire to protect themselves against the advancing thugs. Three from the lunging mob where shot, one died, which caused the riots.