A man who carries a sawed-off shotgun underneath his overcoat robbed another convenience store over the weekend - his fourth hit in a week.

Police officers are still looking for the robber, who was chased Saturday by two men who witnessed him rob the Top Stop at 1080 E. 500 South.Andy Lloyd, of Salt Lake City, told the Deseret News that he and a friend, Marty Bennett, of Los Angeles, were driving eastbound on 500 South when they noticed a man pull a ski mask over his face and walk into the store.

"I knew this guy was going to rob the place," he said.

They turned their vehicle around, pulled in behind the store in time to see the robber put some money inside his pocket.

"He looked back at me and took off running across 500 South," Lloyd said. "He knocked down two people that were on the sidewalk."

The duo followed the gunman into a nearby apartment complex before they eventually lost him. Lloyd said he didn't think about the consequences of chasing an armed robber until after it was over.

"I just felt like it was the thing to do. Stuff like that ticks me off," he said. "It absolutely did not go through my mind that I could get shot."

The same man is believed to have robbed three other convenience stores in Salt Lake City and in the unincorporated county. On Nov. 5, he held up a convenience store while wearing a gorilla mask. Two days later, he robbed a store wearing another Halloween mask. During Saturday's robbery, he wore a yellow and blue ski mask.

In each of the robberies, he wore a long green overcoat and carried a sawed-off shotgun underneath.