Suffolk detectives searched Thursday for the gunman who opened fire on an SUV in Wyandanch late Wednesday -- killing a man and two women and injuring another woman -- in a shooting police say could be gang-related.

"A gunman came upon the vehicle and opened fire," said Suffolk Homicide Chief Det. Lt. Kevin Beyrer, speaking near the scene of the killings on Davidson Street between Cherry and Catalpa streets, several hours after the 11:50 p.m. shooting.

Suffolk police identified the three people who were killed as William Madrey, 25, of Wyandanch; Stephanie Almedina Rivera, 23, of Bay Shore; and Ciara Smith, 23, of Deer Park.

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The fourth victim, whose identity was not released, was taken to a hospital and listed in stable condition.

Beyrer said that Madrey was behind the wheel at the time of the shooting and that his body was found on the ground near the driver's seat. At an afternoon news conference, Beyrer said police are working to determine if gangs were involved and said Madrey has previously indicated he is a member of the Bloods street gang. They did not provide details.

The SUV, a borrowed 2002 Chevrolet TrailBlazer, was parked near a home on Davidson Street where Madrey had moved into the basement about a month ago, according to his mother and girlfriend.

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Police said they hoped to "learn why they were there, what they were doing" in the parked SUV.

Thursday afternoon, investigators processed the SUV and awaited autopsy results to determine if the victims were shot at point-blank range, the number of shots fired, and the number and location of gunshot wounds each sustained, Beyrer said.

This map shows the area in Wyandanch where a shooting occurred that killed three people and injured another on Wednesday, June 3, 2015. Photo Credit: Newsday

Police said the shooter was a male and left the scene. It was unclear whether he was in a vehicle.

"This is what is known to us at this point. This might change as the investigation progresses," Beyrer said.

No drugs or weapons were found in the vehicle or on any of the victims, Beyrer said. K-9 units canvassed the area Thursday morning, but Beyrer would not discuss if a firearm or any other evidence was found.

Residents dialed 911 shortly after the crackle of gunfire -- about a dozen shots -- broke the silence close to midnight.

By dawn, several Suffolk police vehicles and a van from the county medical examiner's office were at the scene. A police K-9 unit examined homes near the SUV as frantic relatives gathered behind police tape at Davidson Street and Troy Avenue.

Suffolk County police on scene of fatal shooting on Davidson Street near Straight Path in Wyandanch at about 12:30 a.m. on June 4, 2015. Photo Credit: Paul Mazza

Stephanie Rivera's mother sobbed as she leaned on the hood of her car.

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"Why would somebody do this to such a sweet person?" said her uncle, Thomas Rivera.

Her older sister, Alisha Rivera, said she wants justice for her sibling although she's not sure she will get it in a part of Long Island where people rarely get involved and are hesitant to talk to police officers.

"When it comes to street stuff, everybody lives by a certain code," she said. "You never know if somebody's going to talk and help. All I know is I lost my little sister."

A detective asked Stephanie Rivera's mother for a description of her daughter's neck tattoo, her uncle Thomas Rivera said.

"They came back and told her it is her," he said. "She's one of the dead."

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Smith's younger sister tried to cross the police line, crying on the phone to her mother, "Mommy, my sister's down there." About 30 minutes later, a woman who identified herself as Smith's mother drove up and asked Beyrer for information about the shooting.

"Please, my daughter might be down there," the woman told Beyrer, saying her first name was Yolanda.

Beyrer told her he would find someone to speak with her. Soon, two detectives arrived and met with the woman. She then collapsed sobbing, into a van parked next to her.

About 8:45 a.m., the gray SUV pocked with holes was hauled away.

By evening, as the sun receded, residents had begun constructing a makeshift memorial outside Madrey's home on Davidson Street.

Hanging on the fence were dozens of candles, red and white balloons and a few bouquets of flowers along with three poster boards signed by friends and family of the dead.

Stone-faced mourners lit candles. Beneath their feet were orange markers where the four tires of the SUV in which the three victims were shot had stood hours earlier.

Beyrer asked anyone with knowledge of the shooting to call Crime Stoppers at 800-220-TIPS. Crime Stoppers is offering a $3,000 reward for any information that leads to the arrest of the person responsible for the shooting.