Christopher Williams, of Queens, killed while walking on Southern State after going missing from Elmont school

A 15-year-old Queens boy who was a student at an Elmont school was struck and killed Thursday afternoon by a motorist on the Southern State Parkway in North Valley Stream, according to state police.

Christopher Williams, who lived in Saint Albans and attended Martin de Porres School for Exceptional Children, was fatally struck around 1:13 p.m. while in the eastbound lanes of the parkway between exits 13 and 14, according to Trooper Brittany Burton, a spokesperson for New York State Police Troop L, which patrols Long Island.

He was transported to Long Island Jewish Valley Stream hospital, where medical staff pronounced him dead, state police said.

The circumstances of the crash, including details about the driver or why the teen was on the parkway, were not immediately made clear. State police are investigating, Burton said.

Williams' family could not be reached.

A spokesman for the school confirmed that the student left the campus during school hours.

Nassau Police Det. Tracey Cabey said the school called police around 1:30 p.m., about 15 minutes after the accident occurred, to report a missing student. Cabey said the school's description of the missing student matched the description of the person police saw on the parkway.

In an emailed statement to Newsday, Joe Trainor, the school's executive director, wrote, "We take this incident very seriously and, working with our board, have already begun a top-down review of our internal procedures and policies.”

Trainor did not elaborate on the circumstances that led to the student being on the parkway.

"The Martin De Porres family is heartbroken at the loss of one of our students, and our entire community is grieving today. We extend our deepest condolences to the student’s family, friends, and loved ones," Trainor wrote.

He said counseling and support services were being made available to students and staff. "We ask for privacy so our school community can grieve and begin the healing process," Trainor said in the statement.

He added: "The mission of The Martin De Porres is to educate children experiencing emotional and behavioral problems, and through that education, we strive for every child to have the opportunity to reach his or her fullest potential. We will always stay true to those core values and put the health and education of our children first."

The three left lanes of the eastbound parkway, which were closed in the area during the police investigation Thursday, were later reopened, according to the state Department of Transportation.