Their mutilated bodies were found at the intersection of Lowell Avenue and Clayton Street in Central Islip, and authorities say one of them was so badly disfigured that he could only be identified through a tattoo. The youngest victim was just 16 years old.
"He had a plastic bag over his head in order to suffocate him," said Yensi Fuentes, victim's cousin. "And from what my cousin saw, his brother saw, they were really, they had a lot of trauma done to their bodies and they were all cut up."
Relatives say the victims were going to the park to meet friends when they were attacked by a group carrying machetes. On Friday, they placed flowers at the crime scene, then stood and embraced one another with tears in their eyes, horrified at the violence that had taken their sons.
The victims were identified as 16-year-old Justin Llivicura, cousins Michael Banegas and Jefferson Villalobos, both 18, and 18-year-old Jorge Tigre. Police believe all four were murdered where they were found.
"He wasn't in it, because I asked him several times and he said no," mother Lourdes Banegas said. "He didn't like the things they were involved in."
Llivicura's mother, Blanca Zhicat, said her son was a quiet, non-violent boy, and she has no idea why he was killed. She thinks he was lured from the family's home with a party invitation on Tuesday and that he left home, reluctantly, that night.
Relatives said the bodies were dismembered, and that Llivicura's ear had been cut off, along with at least one limb. Llivicura's family is from Ecuador and has been in the United States for about 20 years.
Gang violence has been a problem in Central Islip, Brentwood and other Long Island communities for more than a decade, and eight arrests last month in deaths of Brittany Mickins and Kayla Cuevas were the culmination of a long-term sweep by federal officials and Suffolk police targeting gang members.
Earlier Thursday, a group waiting at the scene in Central Islip was hoping for some news about loved ones who had vanished.
Llivicura's family members were among them. They said detectives informed them that police were investigating whether Llivicura was among the dead. His cousin, who didn't want to be identified, said Llidicura told him Wednesday he was going to the park. No one had heard from him since.
"When his parents woke up, he wasn't at home," he said. "So they called his phone multiple times. He never answered. It just went straight to voicemail. The phone was cut off. That's when they got worried, because it was almost like a full day."
Police say this is a gang that preys on the defenseless.
"MS-13, part of their trademark throughout the country not just here, is to prey on recent immigrants," said Commissioner Timothy Sini, Suffolk County Police Department. "Part of that is because many times recent immigrant families are in vulnerable positions."
A $25,000 reward is being offered for information that leads to arrests.
Some family members say there was a fifth young man who escaped the attack.
He would be perhaps the most vital part of this investigation.
The victims' families, meanwhile, have been provided around the clock police protection.
The Associated Press contributed to this report.