Hundreds of grief- stricken adults and kids gathered Friday night at a Brooklyn Little League field to pay tribute to an 8-year-old boy who loved to play baseball — and died in a horrible freak accident.

Kevin “KJ” Reilly, was crushed to death by a heavy concrete window flower planter that fell on him as he climbed the wall of his Marine Park home Thursday to retrieve a basketball that had fallen inside the 4-foot-long box.

“It was a beautiful day and all the kids were playing outside,’’ family friend Jamie Pelicano said.

Pelicano said the youngsters who witnessed the tragedy were “very traumatized.’’

Father Michael Gribbon of the nearby Resurrection Church told the crowd at the Gerritsen Beach field, “We gather to remember him exactly in the place where he celebrated life.’’

Addressing the children at the tribute, Gribbon noted that it’s the place “where he played baseball, where he laughed and played and hung out with you guys and had such a good time. ’’

Kevin is survived by his dad, also named Kevin, his mother, Denise, and two sisters.

“He was really loved by his family,’’ said Dana Donovan, a friend of the boy’s mother. “His mom is such a great mom. It was beautiful to see the community coming together like this to support his family.’’

Another mourner, who asked to be identified as Brian K., said of KJ: “He was very charismatic and made an impression on everyone. He loved sports — baseball, football. He was a Giants fan.’’

A wake was scheduled for Saturday afternoon at Scarpaci Funeral Home in Bensonhurst.