Around 1:30 p.m. Thursday, officers were on Simcoe Street South investigating drug activity in the area.
They tried to arrest a man, but he allegedly punched one of the officers and took off on foot.
After a brief chase, the man was found on Celina Street and arrested.
A loaded gun and some cash were also seized.
Jennoi Mullings, 34, of no fixed address is charged with: assault police, carry concealed weapon, possession of a prohibited firearm with ammunition, obstruct police and weapons dangerous.
He was held for a bail hearing.
Anyone with information is asked to call the Central East Division Community Response Team at 1-888-579-1520 ext. 2188, or Crime Stoppers at 1-800-222-8477 (TIPS).