OTTAWA (AP) _ Four people were killed Tuesday in Ottawa's main bus garage when a man armed with a rifle opened fire on a crowd before killing himself, police said.

Two other people were hospitalized with bullet wounds, police said.

Police Sgt. Sue O'Sullivan said the gunman was a former employee of Ottawa's municipal transportation system, but authorities did not immediately release his name or the names of those killed.

The shooting occurred about 2:50 p.m. in a cavernous garage housing about 500 buses.

A witness said the gunman's rifle jammed or more people might have been hurt.

``It's a good thing that the gun jammed,'' said Sylvain Couture, a mechanic. ``He was coming here to make some trouble. He lost it.''

A transport agency spokesman, Mike Sheflin, said there were about 100 workers in the immediate area of the shooting and there was a rush to get out when the announcement was made to evacuate.

``It's a great trauma,'' he said.

Couture said he saw the man shoot two people inside the stockroom.

``One guy yelled over the PA, `There's a guy with a gun, call 911.'''