(CNN) He was proud of his son for making good grades. So Officer Robert Wilson III climbed out of his squad car in snow-bound north Philadelphia to get him a gift.

While shopping for a game, he died in the line of duty.

Wilson was standing at the counter across from employees at the GameStop store when two brothers, Carlton Hipps and Ramone Williams, walked in carrying guns, police said.

They allegedly stuck up the store with at least five patrons and two employees inside.

'Easy target'

"They said they thought it was going to be an easy target," said police spokesman Capt. James Clark. The store is in a quiet cul-de-sac.

Williams and Hipps had not seen the police car outside, where Wilson's partner Damien Stevenson sat. Nor did they notice Wilson, who was in uniform.

Wilson confronted them, and a firefight broke out, police said.

The officer, an eight-year veteran, stepped away from others in the store to keep them out of the crossfire, police said after watching the store's security camera footage.

30 seconds, 50 rounds

He was a hero and a warrior, Clark said. "He fought until the very, very end, firing at both of them."

Hipps and Williams ducked out of sight at times behind movie posters as they trained their fire on Wilson, Clark said.

Within 30 to 40 seconds, 50 shots fell, he said.

"Officer Wilson was shot multiple times in the body and once in the head. That is the shot that ultimately killed him," the captain said.

Second shootout

With Wilson down, the two men ran out of the store, where Stevenson intercepted them. The officer wounded Hipps in the leg, and Williams ran back inside the store.

He stood around, trying to act like he was just another customer when they arrested him, police said. He later gave them a confession.

Both brothers have been charged with Wilson's murder and with attempted murder on Stevenson.

Street guns, AK-47

The brothers told police that it was their first robbery attempt, but it wasn't their first run-in with the law.

Williams, who is 26, has been arrested twice before, and Hipps, who is 30, six times, police said. He was released from jail in 2009, Clark said.

In the brothers' home, police found an AK-47.

The guns used in the robbery were bought on the street, police said. They want to find out who provided them.

A daughter, a son

At the GameStop, residents have started a memorial, and it's growing, CNN affiliate KYW reported . At the 22nd police district, where Wilson worked, the flag hangs at half-staff.

Actor Dan Aykryod, who was in town on a promotional tour, made a donation to Wilson's family and encouraged others to do the same.

Wilson was 30 years old. In addition to his son, he leaves behind a 1-year-old daughter.

His son turns 10 on Monday. The game was also going to be a birthday present.