Investigators released a picture of the suspect, whose identity still unknown.
Police are desperate to find the suspect, who brutally murdered the four victims during a robbery in Medford. The youngest victim, an employee of the pharmacy, was just 17 years old.
The victims were remembered with a candle light memorial at the pharmacy on Monday night.
The man walked into the Haven Pharmacy on Southhaven Avenue around 10 a.m. Sunday and opened fire, killing everyone in the store. All the victims were shot execution-style, in the head. He left with a backpack full of prescriptions drugs.
"This is a vicious, horrible crime," said Dominick Varrone, of the Suffolk County Police Department. "We are dedicating a great number of resources right now. Our primary interest is identifying and apprehending the individual."
Two of the victims, 45-year-old Raymond Ferguson and 17-year-old Jennifer Mejia, worked at the pharmacy. The other two, 71-year-old Bryon Sheffield and 33-year-old Jamie Taccetta, were customers. Now friends and family are mourning the victims. Mejia was a senior at Bellport High School who planned to attend her prom this week and was looking forward to graduation.
"She couldn't even walk down for graduation," friend Kimberly Jaminez said. "She couldn't even experience a prom yet? They take the innocent ones so young. She was just working."
Jennifer's father is heartbroken, remembering his last conversation with his daughter and her Father's Day message.
"This morning, 10 o'clock, you know, she's supposed to be, she's like, 'I gotta go, I gotta go,' and then she said, 'Happy Father's Day,'" Rene Mejia said. "I say, 'OK, it's OK.' I feel bad because I didn't even hug her."
The quadruple murder has stunned people who live in the quiet community.
Haven Drugs is a well-known business in the suburban neighborhood, and one of the last places residents expected such horrific violence.
In a mid-afternoon press briefing, Suffolk Police Commissioner Richard Dormer denied printed reports of a person of interest in the drug store killings.
Dormer called the crime "one of the most heinous brutal crimes we have ever encountered."
Neighbors say they're disgusted by the senseless murders.
"I'm just so let down about the neighborhood," one area resident said. "It's shocking to me that something like this could happen so close to where I live, especially on Father's Day. It's just an empty, dull feeling."
"It's a small town, it's a family town," another neighbor said. "Everybody knows everyone. Everybody knows the drug store. Anyone who lives in this area, that's where they go."
Police say the suspect is a white male, 5-foot-8 with a thin build. He has dark facial hair and was wearing dark hooded sweatshirt and blue jeans with a black backpack.
Anyone with information is asked to call the Suffolk County Crime Stoppers hotline at 1-800-220-TIPS.