On April 12, the mutilated bodies of four young men were found in a Central Islip park, the latest in a string of what police believe are gang-related murders in the hamlet and neighboring Brentwood.

At the same park on Saturday, children were joyously jumping in a bouncy castle, dancing to hip-hop and playing volleyball while adults got blood-pressure checkups, haircuts and free groceries at a four-hour “free block party” called Hope Day.

Pastor Benny Valle, site coordinator for the event, said the location was picked long before the killings, which “gave us even more of a reason” to hold the festival.

“We felt that the community is desperate for hope and unity,” Valle said.

The Central Islip event was one of 21 Hope Days that were held Saturday in “communities of need” in New York and New Jersey, including 10 on Long Island, said Pastor Mike Taormina of Shoreham, who coordinated the events.

Hope Day began in 2012 with a single event in Uniondale. Missouri-based Convoy of Hope, which has helped spearhead similar events nationwide for years, provides logistical, training and other assistance, Taormina said. Local churches sponsor the events, along with local and national nonprofits and businesses.

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The activities and gifts vary by location and include free food and clothing, dental and medical checkups, family portrait photos, prayer tents and entertainment. Nonprofits set up information booths.

Walter Taylor, 30, held the hand of his daughter Mia, 3, as he arrived at the Central Islip festival.

Taylor, one of more than 1,200 guests of honor estimated to have attended the event, said Hope Day shows the true face of Central Islip, not the quadruple murder that garnered nationwide media attention.

“Since I arrived in Central Islip, I’ve seen nothing but warmth,” he said. “People look out for each other here.”

Rosa Hernandez, 36, who was at the Brentwood Hope Day with her sons, ages 3 and 5, said the area needs more events and programs to keep kids occupied.

“The children need more things to do,” Hernandez said in Spanish as a group of children danced to the 1978 Parliament hit “Flash Light” a few dozen feet away while others waited in line for free Chick-fil-A chicken sandwiches. “If not, kids go from school to the streets and can get involved in drugs and problems.”

The event was a boon to parents like Valerie Skinner, who took three of her children to Adventureland in Farmingdale last week and spent $200.

“This is refreshing to have something free to do with the children,” said Skinner, 43, of Brentwood, who happened upon the Brentwood event with her son Kyree, 5, as they were driving by. “It costs so much to take them out. It’s something for kids to do on a nice day instead of sitting inside doing nothing.”