PENTAGON - Concern about a video allegedly showing an American service member firing into the cab of a civilian truck in Afghanistan has reached the highest levels of the Pentagon.

Defense Secretary Jim Mattis “is aware of the video,” Chief Pentagon Spokesperson Dana White told reporters Thursday.

“CENTCOM (U.S. Central Command) is looking into those allegations,” she added

U.S. news outlet Politico first reported the existence of the video, and officials said the investigation began as soon as they were notified.

The video, uploaded anonymously to YouTube under the title “Happy Few Ordnance Symphony” before it was quickly removed, shows what appears to be a U.S. military vehicle passing a small-cab dump truck, commonly referred to as a “jingle truck.”

The footage then appears to show someone from the military vehicle firing at the truck driver, shattering the driver-side window.

The fate of the truck driver is unknown. And while the investigation is still in its early stages, a U.S. official said if a U.S. service member was responsible, the action would be “deeply troubling.”

Officials who have seen the video said the clip in question lasts no more than a few seconds and appears have been recorded on a helmet-mounted camera. It shows only the forearm, gloved hands and the gun.

U.S. Central Command said in a statement that if any of the video came from U.S. forces, it was neither official nor authorized.

“We take these allegations very seriously,” Joint Staff Director Lt. Gen. Kenneth McKenzie Jr., said Thursday. “This is not something we look at lightly.”

U.S. military officials also emphasized that protecting civilians remains a top priority.

“I can assure you that this video does not represent the professionalism or humanity of the men and women of U.S. Central Command,” U.S. Army Gen. Joseph Votel, the head of U.S. Central Command, said. “We reject the unprofessional and callous message this video conveys.”