An eastern Kansas family is mourning the death of a 3-year-old who was found at the bottom of their backyard swimming pool.

Police say all signs indicate Lucien Mellott of Edwardsville was the victim of a tragic accident, but they’re awaiting autopsy results before declaring a cause of death.

KSHB reports Lucien’s father, Frank, blames himself for forgetting to close a gate leading to the pool.

The boy had lived with the Mellott family since he was 6 months old, but he was legally adopted in March to become a permanent member.

Michelle Mellott says she hopes her son’s death serves as a lesson to others that they need to be diligent at all times so they don’t have to suffer through the same pain she is experiencing.