Police are searching for a gunman who fatally shot a Maine man on an interstate highway in Pennsylvania on Saturday, Fox News reported.

Timothy Davison, 28, called 911 as he entered Pennsylvania from Maryland on Interstate 81, mentioning a heated dispute was happening and that someone had a gun.

Trooper Rob Hicks, a spokesman for the Pennsylvania state police, said officials believe that an unidentified driver in a pickup truck slammed into Davison's SUV, forcing the vehicle to get stuck in a median covered in snow along the road. 

After the crash, police said the gunman got out of his truck and fired "multiple shots" into the SUV. Shortly after being rushed to the hospital, Davison was pronounced dead.

He was driving back home to Portland, Maine after visiting his sister for the holidays in Orlando, Florida.

"I think we can call it a road rage incident," Hicks said. "At this point we haven't found anything that would connect the two men."

As of Sunday night, no witnesses have come forward with information and no one has been arrested. The Federal Bureau of Investigation (FBI) is now involved in the case.

Hicks told the Kennebec Journal that authorities are searching for a dark-colored pickup truck, possible a Ford Ranger, with some damage to the driver's side. Police also said they're searching for bullet fragments with hopes of identifying the gun's owner.

The state trooper added that the incident may be connected to a shooting that occurred one day earlier involving a pickup truck in Monaghan Township, Pa., about 30 miles from Saturday's shooting.

Davison's mother, Theresa Allocca, said on Sunday that she wants her son's killer to be brought to justice.

"I just hope this doesn't happen to anyone else. This wasn't just road rage. This person is obviously crazy," Allocca said.

Anyone with information on the investigation is asked to call the Pennsylvania State Police at (717) 264 - 5161.