JERSEY CITY - A young police officer was killed while responding to a report of an armed man at a Jersey City Walgreens store early Sunday morning, and the suspect was also killed.

It happened at the store on Communipaw Avenue. Authorities say Officer Melvin Santiago was shot in the head as he sat in his patrol car with another officer  shortly after 4 a.m.

Santiago, 23, was pronounced dead shortly after arriving at Jersey City Medical Center, according to Jersey City Mayor Steven Fulop. He had just joined the force in December, according to the mayor's office.

The crime was initially believed to be an armed robbery, but now officials say it appears the suspect was out to shoot and kill police officers.

Officials say the suspect, identified as 27-year-old Lawrence Campbell, entered the store with a knife. Campbell allegedly assaulted an armed security guard and took his gun. While someone in the store called police, the suspect allegedly waited outside for police to arrive.

As he waited for police, the mayor's office says the suspect told a witness to "watch the news" because he was "going to be famous."

A police vehicle arrived at the scene with Santiago and another officer inside. Campbell fired into the car at close range, fatally striking Santiago in the head. It is believed that he used the security guard's gun in the shooting.

Campbell then fired shots at a second marked police car, striking the windshield. Those officers were not injured. One of them returned fire, fatally striking the suspect.

Officials say there were seven customers and several store employees in the 24-hour store when the incident began, but they were not hurt.

Investigators say Campbell was one of three suspects wanted in connection with a prior homicide in Jersey City. They are still searching for another suspect in that case, identified as Daniel Wilson.

In a statement, Fulop said Santiago was "an officer who represented everything one would want to see in a police officer." He added, "I know the entire city's thoughts and prayers are with the Santiago family at this time, and we mourn together."