LEWISBERRY, Pa (AP) — A truck driver fell asleep at the wheel before striking a construction vehicle and killing three workers on the shoulder of a Pennsylvania highway in April, authorities said Friday.

Pennsylvania State Police said the 24-year-old driver from Roxbury, Massachusetts fell asleep on Interstate 83, about 8 miles (13 kilometers) south of Harrisburg on April 17.

Investigators said the man was driving a large box truck at about 3:25 a.m. when it struck a construction vehicle in a work zone, then hit the three workers on the shoulder.

Killed were Jesse McKenzie, 24 of Rockwood, Pennsylvania; Philson Hinebaugh III, 24, of Johnston, Pennsylvania; and Robert Hampe, 41, of Meyersdale, Pennsylvania.

The driver was not injured.

A State Police spokesman said a decision on whether to file charges in the case will be made once the investigation has been completed.