Four people killed during a pharmacy store robbery in suburban New York City, including a teenager due to graduate high school this week, were shot at very close range by a dangerous suspect intent on stealing painkillers, a police official said Monday.

Suffolk County Police Commissioner Richard Dormer also warned physicians and the owners of small drugstores in the area to be vigilant about anyone "expressing an urgent need for prescription painkillers." He said added police patrols would be deployed near small pharmacies until a suspect is apprehended.

Dormer called Sunday's killing at the Long Island pharmacy "one of the most heinous, brutal crimes we have ever encountered."

The shootings happened at about 10:20 a.m. inside Haven Drugs in Medford, a family-owned pharmacy in a small cluster of medical offices about 60 miles east of New York City. Police identified the two employees who were killed as pharmacist Raymond Ferguson, 45, of Centereach, and store clerk Jennifer Mejia, 17, of East Patchogue.

Bryon Sheffield, 71, of Medford, and Jamie Taccetta, a 33-year-old woman from Farmingville, were identified as customers who were also slain.

"The victims whose lives were cut tragically short were killed for no apparent reason and without warning," Dormer said. "They offered no resistance and did not appear to provoke the assailant. They were all shot at close range."

The suspect appears in still photographs from the video released by police; he's a gaunt man in his late 20s or early 30s, about 5-foot-8 with a thin build. He has dark hair, was unshaven or has a dark beard and mustache and wore a dark hooded sweat shirt, dark pants and a white baseball cap.

He stole painkillers and killed everyone in the shop before fleeing with a black backpack.

Police have offered a reward of up to $5,000 for information leading to the arrest of the man, whom detectives described as "extremely dangerous." Dormer said the department had already received a "substantial number of tips which detectives are working on right now."

Dormer described the quality of the video, which was not released, as "excellent video and it's a good view of what happened." He said the four victims were shot at close range "very suddenly and very quickly ... over a few minutes."

The veteran officer, who came out of retirement to be police commissioner in 2004, was asked to compare the killing to others he has investigated.

"You have four innocent people, two workers on a Sunday morning in a nice, quiet neighborhood and died viciously and violently. Two customers walk into the store, they're not thinking it's their last day on earth and they're killed. This is very unusual."

He said there had been no apparent robbery pattern involving pharmacies preceding Sunday's massacre.

Mejia, who worked part-time at the pharmacy while attending Bellport High School, was due to graduate Thursday. Friends at the shooting scene Sunday described her as "a walking angel on earth." Others said she was planning to attend community college next year.

Bellport High School assistant principal Brian Norton said Monday that grief counselors were available for students.

"She was an absolute sweetheart," he said. "A very lovely young lady looking forward to her future."