UPDATE: Slain Jersey City Officer's Funeral Set for Friday

A Jersey City police officer was shot in the head and killed early Sunday by a man who told a witness he was "going to be famous," Mayor Steven Fulop said.

Officer Melvin Santiago, 23, was in the first police car to arrive at the scene of a reported robbery at a 24-hour drug store. He was shot through the vehicle's open door, Fulop said at a news conference.

Police had been called to the scene at around 4 a.m. after a man entered the store, asked for directions to the greeting card aisle, walked around, then punched a security guard, the mayor said.

The man, who was carrying a knife, didn't steal anything but waited for police to arrive. At one point, he apologized for his behavior and told a witness outside of the store: "Watch the news later, I'm going to be famous," Fulop said.

Then, when the first marked car arrived, he started shooting with what police believe was the guard's weapon.

Other officers arriving at the scene returned fire, and the shooter was killed. Santiago was declared dead at Jersey City Medical Center.

"He didn't even have time to defend himself," said the officer's anguished mother, Cathy McBride. "This guy snuck up and shot him through the window and killed him instantly."

Fulop identified the shooter as Lawrence Campbell, 27, one of three suspects wanted in an earlier killing in Jersey City. A second suspect in that killing was arrested on weapons charges Sunday night.

Santiago, who grew up in Jersey City and attended community college, had joined the force in December. Fulop said a commander had taken him out for pizza just last week and joked with him that he should smile more.

Santiago is the first Jersey City officer killed in the line of duty since Detective Marc DiNardo died in July 2009 during an apartment raid to search for suspects in a robbery.

"It is a tragic situation when any officer is killed in the line of duty," Fulop said in a statement. "Melvin was an officer who represented everything one would want to see in a police officer. I know the entire city's thoughts and prayers are with the Santiago family during this difficult time."

Jean Belviso, who has been delivering newspapers for 10 years, said she was driving through the Walgreens parking lot when she said saw a man wearing burgundy sweatpants and a baseball cap walk out of Walgreens. A police cruiser pulled up in front of the store, and the suspect began shooting, the 61-year-old Belviso said.

"We thought he was running, coming toward us," said Belviso, who was riding along with a friend. "He kept on shooting."

Bullets flew through the cruiser's windshield; other police cars appeared on scene, and officers fired at him, Belviso said. The suspect was shot multiple times, and officers slapped handcuffs on him, she said.

Campbell's body remained on the ground next to the bullet-riddled cruiser for more than five hours after the shooting before it was placed in a coroner's van and taken away.

Markeisha Marshall, a spokeswoman for Walgreens, said the company was "deeply regretful" over the officer's death and extended its sympathies to his family and friends. The store has round-the-clock armed security, Marshall noted.

The Jersey City Police Benevolent Association said in a statement that their hearts were heavy over Santiago's death.

"Patrolman Santiago knew the risks associated with this job, yet he put himself in front of danger in order to keep Jersey City safe," the association said. "Words cannot adequately express our feelings about this senseless tragedy."

McBride said her son was "an amazing man, he was the love of my life. He was 23 years short, and I'm empty right now."

The officer's stepfather, Alex McBride, said Santiago was "very proud" to be a police officer, following in the footsteps of his uncle. McBride said he had been in Santiago's life for 14 years, noting that his stepson had wanted to be a police officer since playing the "Call of Duty" video game.

"Melvin was the best kid," he said, choking up as he sat hunched over on a plastic crate in an alley outside the family's apartment. "I watched him graduate from high school. He joined every sport, everything. He never did no harm to nobody. And he was full of life."

Gary Nahrwold, 24, recalled Santiago first saying a decade ago that he wanted to become a police officer. Nahrwold also hopes to join the force and said he won't be discouraged by his friend's death.

"It just gives me more purpose to do it," he said. "I'm not going to be deterred by some senseless crimes."