WATERLOO — Heavily armed tactical officers surrounded 12-unit apartment building in Waterloo on Saturday afternoon, after citizens and police reported gunshots.

But about two hours later, Waterloo Regional Police determined it was someone who had repeatedly slammed a door inside one of the apartments in the building in the 400 block of Hazel Street, near Smallwood Drive.

Nobody was hurt. No charges were laid, said Staff Sgt. Deborah McBride.

"Apparently there was a heavy door that, when it was slammed, sounded just like a shotgun," McBride said.

"The officers who arrived heard it."

Police were first called at 1:40 p.m. after tenants in the building reported gunshots. When officers heard similar noises, they surrounded the three-storey building and called for backup.

At least 10 police cars raced to the area of Hazel Street north of Columbia Street to cordon off the area. Then tactical officers arrived to take over.

When they entered the building about 4 p.m., they detained a man but didn't find any evidence of gunfire.

"We don't know who slammed the door, but we don't think there was malicious intent," McBride said.

Public safety concerns prompted the big police response, she said.