LONDON, ONT. -- Woodstock police flooded the city's downtown Wednesday following a robbery involving a knife at a Dundas Street business.

Harold Van Amerom, the owner of Gizmo Direct, tells CTV News a man trying to sell a phone came into his store around 12:45 p.m.

After repeatedly expressing concern the phone was stolen, Van Amerom says the man grabbed another customer's phone and fled.

He says he chased the man onto Wellington Street North, at which point the man became agitated and "pulled the knife out."

That's when things changed, Van Amerom says, "[He] turns around, grabs the knife and says something like, 'Let's do this.' And he's waving his knife at me, so he is pretty much trying to slice me at that point."

Van Amerom then backed off and police were called. No one was hurt in the altercation.

He says in eight years of business, this is his first robbery.

Several Woodstock police units were called in after the robbery to assist, including uniformed officers, the K9 unit and the Forensic Unit.

The suspect fled north on Wellington Street. He is described as white, about five feet ten inches tall, with a slim build and dark hair, wearing a black coat, black ball cap and a red shirt, and carrying a black backpack.

Woodstock police say nearby schools were advised of the situation as a precaution.

Anyone with information on the incident is asked to contact police at 519-537-2323 or Crime Stoppers.