The two children had been missing for about an hour when their mother called 911 worried about their whereabouts. Police descended on the area, canvassing the neighborhood until an officer saw a shoe floating in the uncovered pool.
"He entered that backyard by jumping over a fence," Suffolk police detective sergeant Edward Fandrey said. "With the assistance of another police officer, they jumped into the pool. And in a short period of time, they recovered the lifeless bodies."
Ralph Knowles, 5, and his 7-year-old sister Sharon were found around 3:30 p.m. in the backyard of the home on Half Mile Road.
The children were taken to Southside Hospital in Bay Shore, where they were pronounced dead.
Earlier in the day, a neighbor had reportedly seen one of the children climbing a tree and peering over a fence into the neighbor's backyard.
The owner of the home has been cited by the town for improperly installing the fence in their backyard. It was put in with the smooth side in, with the ladder like side facing out, which made it easier for the children to climb over.
The mother of the children insisted Monday that she was a conscientious parent who thought her children were safe playing in their yard.
"Right now, I have everyone looking at me as the mother and wondering what happened," Tia Knowles told a small group of reporters while sitting in a neighbor's house down the street from where she lived with her children. "I watch my children carefully but due to the split second, the time I wasn't watching them, unfortunately they got into my neighbor's yard and they got into their pool."
Neighbors and friends of the two young children were at a loss Monday to understand how the tragedy unfolded. It is not clear anyone saw the children in the moments before they gained access to the pool.
Although the tragedy occurred on a sunny spring day, swimming pool season on Long Island doesn't ordinarily begin until near Memorial Day. Nevertheless, the pool where the children died was in no condition for recreational swimming.
"That very much bothers me; that they were able to have access to that pool," said Mitchell Olshwitcz, who identified himself as a family friend. He described Ralph and Sharon as "great kids. They liked to get into everything, obviously."
The home where the children lived is owned by a nonprofit that provides housing to homeless families, Birbiglia said. What appeared to be a Barbie doll could be seen on the roof of the one-story ranch where the family lived.
(The Associated Press contributed to this report.) ---