Two employees at a Spenard sandwich shop detained a would-be robber Tuesday morning after the man said he had a gun and demanded money, Anchorage police said.

A caller at the Subway store on West Northern Lights Boulevard reported the robbery to 911 dispatchers at 9:52 a.m., said police spokesman Lt. Dave Parker.

"Within about 30 seconds, we get the call back that the employees had him down on the ground," Parker said.

Police said Alvin L. Archa Jr., 48, walked in the store, put his hand in his pocket and claimed to have a gun. When he demanded cash, two employees came out of the back of the store and grabbed him, Parker said.

"We don't always encourage people to do that, but we try to encourage people only to act and react as the circumstances surrounding the robbery require," Parker said.

Police arrived a few minutes later and arrested Archa. He did not have a gun, Parker said.

Archa is charged with first-degree robbery and his bail was set at $25,000. He was also arrested on a no-bail warrant for violating conditions of his probation. According to court records, Archa pleaded no contest to first-degree robbery in 2005.

Parker said it's unclear if Archa -- described as white -- was involved in two previous Subway robberies in the past two months. In those cases, the suspect was described as a younger, black male. Still, detectives will be looking into whether Archa was involved in those thefts, Parker said.

All three robberies occurred about the same day of the month.

On August 4, a man robbed the same Spenard store and pistol-whipped a male employee before leaving, police said. On Sept. 3, a man wearing new-looking ski gear robbed the Subway on Northway Drive, taking cash and hitting a female employee with a gun, police said.

Reach Casey Grove at casey.grove@adn.com or 257-4589.