Police have arrested a man they were chasing after the suspect ran into a building that was hosting an NDP rally.

NDP Leader Jack Layton was speaking at the event, taking place in the Bloor Street and Lansdown Avenue area. However, police say the party leader had just left the rally when the incident took place.

Authorities say they chased a suspect after they spotted a handgun being thrown on the ground outside the building.

A suspect fled into building and after a scuffle with police, an arrest was made.

An officer was punched during the altercation but only suffered minor injuries, said authorities.

The gun, described as a silver pistol, was partially concealed in a cell phone case.