A Riverside man died hours after he and a second victim were shot early Friday morning by a man dressed as a robber at a Halloween costume party at Dream Nightclub in Hampton Bays, according to the Suffolk County Police Department’s Homicide Squad.

Carlo Petrusa, 64, was declared dead at Brookhaven Memorial Hospital Medical Center in East Patchogue, where he was taken by Hampton Bays Volunteer Ambulance following the 3:47 a.m. shooting on October 29, according to Suffolk County Police Department Homicide Squad Detective Sergeant Lamb.

Homicide detectives are still searching for the gunman, who fled the scene immediately after the shooting.

According to Southampton Town Police, the shooting occurred early Friday morning following a costume party at the nightclub.

“There was a fight at the club between contestants,” said Town Police Detective Sergeant Randy Hintze, regarding the costume contest. “Numerous subjects were involved, both inside and outside the club, and all were engaging in physical fighting.”

The second victim­—Shawn Badgett, 35, of Coram, a promoter for the event—was also shot by the same gunman during the brawl, according to police. Town Police said Mr. Badgett was transported by friends to Stony Brook University Medical Center for treatment and released later the same day. No other injuries were reported, according to police.

Authorities said the gunman was dressed as a character from the 1995 movie “Dead Presidents,” a film about a group of Vietnam veterans who dress in all black clothing with white face makeup while attempting to steal money that is scheduled to be taken out of circulation.

According to James Vlahadamis, the son of the family that owns the club as well as the Hampton Bays Diner on Montauk Highway, Mr. Petrusa had just moved from his home on Springville Road in Hampton Bays to MacLeod’s mobile home park off Riverleigh Avenue this summer. He also said that Mr. Petrusa, who many people referred to as “Uncle Carl,” was a former New York City Police Department court officer who worked as a bodyguard for celebrities.

He said that Mr. Petrusa, who was not married and has no children, was not working at the nightclub at the time of the shooting, though he sometimes worked security at the establishment. According to Mr. Vlahadamis, Mr. Petrusa was at the club “hanging out with my dad,” Frank Vlahadamis, on the night of the shooting. He said his family does not know why Mr. Petrusa was standing outside the club at the time.

Town Police said a fight broke out inside the nightclub between a contestant dressed as a cave woman and another contestant wearing an unknown costume. The fight moved to the outside of the club, and police said a man dressed as a character from the movie “Dead Presidents,” but who wasn’t a contestant in the nightclub’s costume contest, ran to the parking lot, retrieved a handgun from his car and discharged several rounds while approaching the nightclub’s entrance.

Mr. Vlahadamis said his father was at the club at the time of the shooting and that Mr. Petrusa was struck twice by bullets, once in the abdomen and once in the buttocks. He said that he and his mother, Maria Vlahadamis, received a call from the hospital at around 1:50 p.m. on Friday informing them that Mr. Petrusa’s condition was worsening. Mr. Vlahadamis said he learned that Mr. Petrusa had died when they arrived at the hospital later that day, adding that one of the bullets had struck Mr. Petrusa close to an artery.

“We literally saw this man every day of our lives,” Mr. Vlahadamis said, adding that a moment of silence was observed last Friday night at Dream Nightclub in memory of Mr. Petrusa. “We’re devastated,” he said, later adding, “We were as close to family as we could be without being related by blood.”

“Uncle Carl was a beautiful man,” added Paul Tully, a longtime friend of Mr. Petrusa who recently moved from Hampton Bays to upstate New York. He said both he and Mr. Petrusa used to work security at local nightclubs. “He was everybody’s Uncle Carl,” Mr. Tully added.

In May, Mr. Badgett, the second shooting victim, was one of 20 people arrested following a nine-month investigation targeting heroin traffic on eastern Long Island. At the time of his arrest, detectives found more than $60,000 in cash inside his Coram home, another $90,000 in cash in a safe deposit box, as well as heroin, scales and bags, according to the Suffolk County District Attorney’s office. Mr. Badgett was charged with multiple felonies, including second-degree and third-degree criminal possession of a controlled substance, according to police. He was free on bail at the time of the shooting.

The drug bust, which included 19 other arrests, resulted in the confiscation of 4,430 bags of heroin packaged for street sale and almost $175,000 in cash, according to authorities. At the time, the DA’s office said the ring helped transport 2,500 bags of heroin per week from New York City suppliers to drug dealers on eastern Long Island.