A North Philadelphia man was killed Sunday night outside a corner grocery store as he tried to catch a man who had just shot the store owner.

Police described 26-year-old Rafael Santiago DelValle as the "Good Samaritan" in a robbery at La Familia Latina, a mini-mart in the 3500 block of North Fifth Street.

Police had initially identified the dead man as a bandit involved in the shooting, but investigators said Monday that DelValle was in fact the victim and a friend of the store owner.

Initial reports that there were four robbers involved were incorrect. Police have identified two men involved in the robbery and are circulating a photo of a third man.

Police said that at 8:25 p.m. Sunday, Edward Friedland, 26, entered the La Familia Latina and tried to hold up the store. The owner, Antonio Monegro, 39, pulled out his own gun in defense. Shots were exchanged, with one hitting Monegro in the stomach, police said.

Friedland fled the store as Monegro lay on the ground inside. Both guns had been dropped on the floor.

Police said DelValle picked up Monegro's gun and chased Friedland out of La Familia - a decision that would cost him his life.

DelValle did not realize as he ran onto Glenwood Street that another man was still in the store, according to a relative of DelValle's.

Wearing a blue baseball cap and white T-shirt, the unidentified man grabbed Friedland's gun and followed DelValle, police said. He shot DelValle multiple times in the back before standing over him and shooting him one last time in the head at Fifth and Glenwood, less than one block from the store.

Police responded to the shooting at 8:28 p.m. and pronounced DelValle dead at the scene.

Philadelphia Police Capt. James Clark, commander of the homicide unit, said at a news conference Monday afternoon that police believed the unidentified man was an accomplice and possibly a lookout in the store. They are offering a $20,000 reward for anyone with information about the man, described as 18 to 25 years old and Hispanic.

Friedland was able to flee the scene with the help of a third man, who drove him to Frankford Hospital in a gold Buick, police said. Police have identified and questioned the third man, but he has not been charged with any crime, and police have not released his name.

Clark said at the news conference that Friedland is in critical but stable condition. He is under police guard at the hospital and will soon face charges.

Monegro, who was taken to Temple University Hospital, is expected to survive, said his brother, who would not give his name.

Police said nothing had been stolen from the store. La Familia Latina was closed Monday, but neighbors outside expected it to reopen Tuesday.

"When I heard it on the news, I thought, I go to that store all the time. It's my favorite store," a neighbor said on the sidewalk in front of La Familia Latina on Monday afternoon.

There are no funeral plans yet for DelValle. Andres Colon, DelValle's brother, said his mother and two other brothers are coming from Puerto Rico.

Colon shrugged his shoulders and said he was not surprised by Sunday night's robbery and shooting.

"This happens all the time," he said through a neighbor who translated from Spanish.

Contact Liz Gormisky at 215-854-5626 or lgormisky@philly.com.