Boy locked in toilet before death plunge

THE 5-YEAR-OLD boy who fell to his death in Queens on Sunday was unable to open a bathroom door because of a faulty lock — so he made a fatal attempt to climb out a window, police said Monday.

Little William Chen was visiting the family-owned, three-floor apartment building — which is under renovation — in Corona and was in the care of his grandparents, Ting Bao Chen and Yan Pan Sheng, police said.

They were on the second floor when William went into a thirdfloor bathroom of the home on 37th Ave. and 99th St., police said. The lock on the bathroom door was installed backward, trapping him inside.

William crawled out the bathroom window at about 2:40 p.m. but slipped and fell, landing on a set of stairs leading to the building’s basement, witnesses said.

The boy was rushed to New York-Presbyterian Hospital Queens, where he died.

Cops do not suspect criminality.

“It’s horrible what happened . . . His mom is not doing well,” a family friend said.