A man and woman from Alpha were in the vehicle when the incident occurred, according to investigators.
A bullet shattered the window of an SUV on Monday evening on Interstate 78 in Williams Township, Pennsylvania State Police said.
A 41-year-old man and 47-year-old woman, both from Alpha, were in the Honda CRV when the incident occurred about 6 p.m., according to state police at Belfast.
The pair were headed east in the right lane of I-78 and pulled over on to the right shoulder to dial 911, in the area of mile-marker 74.7, police said.
Police did not elaborate on any evidence of gunfire found.
Police officer killed in I-78 crash
Police were continuing to investigate and asked anyone with information that may be of use to call state police at 610-759-6106. The incident number to reference is PA17-570135.
Kurt Bresswein may be reached at kbresswein@lehighvalleylive.com. Follow him on Twitter @KurtBresswein. Find lehighvalleylive.com on Facebook.