CHICAGO (CBS) – The 41-year-old Chicago police officer who was fatally shot Thursday evening was described in glowing terms by grief-stricken admirers.

Clifton Lewis was pronounced dead at about 9:30 p.m. Thursday after he was shot at an Austin neighborhood convenience store where he was working off-duty as a security guard. Police say Lewis tried to prevent an armed robbery by two masked men.

Lewis, who lived in the West Side neighborhood, had only recently taken the side job, according to Henrietta Fountain, the grandmother of the officer’s 11-year-old daughter, Simone.

She told reporters that Lewis was a “workaholic” who loved being a Chicago police officer. He was engaged to be married, Fountain confirmed.

“All he thought about was his job and his daughter,” she told reporters outside Lewis’s West Side home.

“He was the best. He loved her completely and he would do anything for her, sometimes too much,” she said. “He was always there for her and the family.”

Lewis racked up 81 commendations during his eight-year tenure on the force. He was a member of the Austin District Tactical Unit.

Deputy Police Supt. Al Wysinger described Lewis as “a gentle giant” who had a “courageous heart.”

He “loved his family, loved this community,” Wysinger said during a Friday news conference to ask for the public’s help in solving the killing.

Fountain said she had left a message with Lewis earlier Thursday, saying he could pick up his daughter for the week and also pick up some Christmas gifts.

“I was surprised why he didn’t return the call. He usually returned the call right away,” she said.

Police called Lewis’s daughter after he was shot and arranged to have police take her and Fountain to the hospital. Instead, detectives showed up at their home to break the sad news, the grandmother said.

At the 15th District station where Lewis worked, the Chicago city flag came down, and the Gold Star flag of mourning went up, flying at half-staff.

On the Austin block where Lewis lived for the past couple of years, neighbors expressed sadness. Donald Page says he broke down in tears when he heard the news.

“I considered him like a son, so to speak,” Page told CBS 2’s Derrick Blakley. “I greeted him when he first moved on the block a couple of years ago. He seemed like a real nice guy. Then I found out he’s a police officer — that was even better for the neighborhood.”

“He was OK,” another neighbor, Derry Chambliss, said. “He walked his dogs, he spoke. I didn’t even know he was a cop for awhile, until I seen him in uniform.”