11/05/2012 04:17 EST | Updated 01/05/2013 05:12 EST

Convicted cop killer on the run, has gun, has robbed grocery stores: police

QUEBEC CITY, Que. - A convicted cop killer who disappeared from a Montreal halfway house is on the loose and police said Monday that he has already committed two armed robberies.

Pierre Ouellet didn't return to a home in Montreal last week and, according to police, he swiftly obtained a handgun and robbed a pair of Quebec City grocery stores on Thursday and Friday.

Ouellet was sentenced to life in prison for the 1986 slaying of a Montreal police officer, Claude St-Laurent.

He had been pulled over and was able to disarm the constable before shooting him with his own service revolver near Montreal's Olympic Stadium.

A quarter-century behind bars has failed to rehabilitate him, according to police.

Quebec City police said they had surveillance video showing him brandishing a gun at the grocery stores. They called him armed and dangerous.