WESTBORO (CBS) – A young boy died who after falling into in a swimming pool in Westboro over the weekend had pushed out a screened window and walked away from his family’s first floor apartment, investigators said Monday.

Four-year-old Alexie Lepoer was reported missing shortly before 5 p.m. Sunday and was found about a half-hour later in the murky water of the swimming pool at the Park Village West apartment complex on Main Street.

He was rushed to UMass Medical Center in Worcester, where he was pronounced dead.

In a statement issued late Monday morning, Worcester District Attorney Joe Early Jr. said the boy had severe autism and was likely carrying a cordless phone that he used as a toy.

That phone and a diaper were found near the fenced-in pool. The gate was locked, according to Early, and visibility in the pool was less than two feet.

The pool had not yet been opened for the season.

The medical examiner’s office will officially determine how Alexie died.