JACKSONVILLE, Fla. -- Loved ones are mourning the loss of a 3-year-old boy after his body was found in a water tank at Bruce Park in Arlington.

The Jacksonville Sheriff’s Office said they discovered Amari Harley's body after he went missing during a birthday party Sunday afternoon.

Police said they found his body before 8 p.m. Sunday inside of a water tank underground. Investigators have not released exactly how Harley ended up in a water tank.

Family believe the boy somehow got through a plastic lid that once covered the tank. City crews have since replaced those covers with screwed in wood covers.

On top of those new covers now rest balloons and flowers from mourning friends and family.

"This is an innocent baby, and we would never ever forget him," said family member Janice Douglas.

Kamilla Jenkins, one of the boy's cousins, stopped by Monday to pay her respects. Through tears, she said she's still puzzled how this could have happened.

Jenkins said family realized something was wrong in the afternoon when Harley was nowhere to be seen.

"He was a kid, a boy," Jenkins said. "Football, you know, he thought he was one of the bigger kids, he liked to hang with the bigger boys."

Even those that didn't know the boy stopped by to pay their respects.

"It's sad and it hurt me," said John Glenn of Arlington. "I was up all night just thinking this little boy, this poor little boy."

Neighbor Janice Levett helped family look for the boy Sunday night.

"I'm praying for the family and I hope the family gets through it," Levett said.

Levett distinctly remembers there being removable plastic covers on the holes that lead to the water tank.

"The city needs to fix that, they need to fix that so it doesn't happen to another kid," she said.

Family is now left with similar questions.

"Why wasn't it secure?," Jenkins asked. "I mean, even if there was a cover on it, obviously it was able to be moved by one of us when it should have, I feel like, taken some special tool for it to be removed."

Police said they believe that there are more people with pertinent information to the investigation. They request that anyone who was at the park around the time that Harley went missing to contact the police.