He showed no mercy.
He then loaded his backpack with prescription painkillers and fled Haven Drugs pharmacy. He was in and out in just a few minutes.
"This is one of the most heinous, brutal crimes we've ever experienced," Dormer said at a news conference.
In search of a killer
Authorities Monday night were still trying to find the killer, who they believe is a drug user, as a manhunt continued across the region. Police implored the public to help identify a bearded young man caught on surveillance video wearing a white baseball cap, sunglasses, sweatshirt and black backpack.
Fuller portraits also emerged of the four victims: Raymond Ferguson, 45, of Centereach, who worked at Haven part-time as a pharmacist; his assistant, Jennifer Mejia, 17, of Medford, a high school senior; Bryon Sheffield, 71, of Medford, a husband picking up drugs for his wife's heart ailments; and Jaime Taccetta, 33, of Farmingville, a single mother of two engaged to be married.
Grief and anger rippled through their central Suffolk communities. A memorial of flowers and candles was created outside the one-story medical office building off Route 112 that houses Haven. At Bellport High School, where Mejia was a senior, flags were flown at half staff. Counselors comforted heartbroken classmates.
"God will take care of it," said Mejia's father, Rene, outside his home Monday. "We are no one to ask for revenge. All we can do is pray."
Deadly moments on video
The ruthless slayings were clearly captured on chilling surveillance video, Dormer said.
The suspect -- his sleeves rolled up, armed with a handgun -- walked into the family-run pharmacy shortly after it opened and started with the employees. He first opened fire on Ferguson and Mejia, killing them "very suddenly and very quickly," Dormer said, and "for no apparent reason."
He then turned to the customers, Sheffield and Taccetta. Police would not say if they were in the store when the shooting began or entered as it unfolded.
"Two customers walk into the store, they're not thinking this is their last day on Earth and they're killed," Dormer said.
The suspect was last seen running east on Southaven Avenue. The 911 call came in at 10:23 a.m.
"Our hearts go out to the families and friends of the four victims of this senseless, brutal crime, and we pledge to them that our police department is working tirelessly on bringing this suspect to justice," Suffolk County Executive Steve Levy said in a statement.
Investigators have seized on the suspect's ostensible goal -- the theft of addictive synthetic opiate painkillers -- as an essential clue.
Suffolk parole and probation officials Monday looked in their records for leads: known opiate addicts or someone who might have recently failed a drug test. Narcotics detectives consulted informants to learn if opiate pills were hitting the black market en masse. "We believed the suspect is a drug user and should be considered armed and dangerous," Dormer said.
Criminal intelligence officers were also going through casework and examining the surveillance video. All commands and precincts in Suffolk and Nassau police received photos of the suspect.
Meanwhile, Suffolk deployed more officers near pharmacies and put plainclothes crime section officers into uniform to make a more visible presence, Dormer said. He appealed to doctors and pharmacists and anyone who has encountered someone "expressing an urgent need for prescription painkillers" to examine the photos.
"We're asking those who work in pharmacies, especially smaller stores off the beaten track, to be extra vigilant," he said.
Plea to the public
Police are asking the public to call Crime Stoppers at 800-220-TIPS. All calls will remain confidential and callers are eligible for a cash reward of up to $5,000 for any information leading to an arrest. Suffolk CrimeStoppers board president Nick Amarr said the phone lines were "flooded" Monday with tips.
The shooting was the third crime in 19 months at Haven, police said. There was an unsuccessful burglary in January. In December 2009, a man in his 20s robbed the business of cash, but no drugs were taken and no one was hurt. No arrests were made in either case.
The pharmacy owner, Vinoda Kudchadkar, installed security cameras last month in response to the earlier crimes, said friend Soma Pulipati, a cardiologist in the plaza. "But, see, cameras don't prevent these things," Pulipati said. "They only help after."
With Matthew Chayes, Mikala Jamison, Bart Jones, Tania Lopez, Víctor Manuel Ramos, Patrick Whittle, Olivia Winslow and Jennifer Smith