Three men and a 15-year-old boy have been arrested in connection to the killing of an 18-year-old man found in a Bellevue park in April, the Bellevue Police Department said Tuesday.

Bellevue police responded to reports of gunshots coming from Goldsmith Neighborhood Park around 12:30 a.m. April 3. They found Josue Flores dead with multiple gunshot wounds, the first murder in the city in more than three years, according to a statement from Bellevue police.

Police believe the suspects knew Flores, who told his friends he’d received threats from members of the suspects’ group, said Bellevue Police Chief Steve Mylett. Flores told people he was going to the park to meet with the group and smooth things over, but he was ambushed, Mylett said. He said police believe two of the suspects fired at Flores.

Police used Snapchat and text messages to build their case against the suspects, as well as photos on social media showing the suspects throwing gang signs and posing with firearms, Mylett said. Police also located a handgun believed to have been fired at the park, he said.

Mylett said police also linked the suspects to a shooting in Everett on the same night that injured a 17-year-old boy.

The three adult suspects were arrested separately: One was arrested in a traffic stop in Renton, another after a traffic stop and short foot pursuit in Bellevue, and the third outside Bellevue District Court, where he appeared for an unrelated case. They were booked into the King County Jail on investigation of homicide.

The 15-year-old boy was arrested Tuesday after he was released from the King County Youth Detention Center. He was booked there again, on investigation of homicide, according to police.

The suspects are expected to appear in court Wednesday afternoon.