(ABC News) -- A man killed during an alleged road rage incident made repeated 911 phone calls as he tried to evade his pursuer, according to police.
Timothy Davison, 28 was driving through Pennsylvania on Jan. 4 on his way home to Poland, Maine, when he was shot to death. Police have said they believe another motorist, in a fit of road rage, pushed Davison's car off the road and then shot him multiple times in his incapacitated car.
Davison initially called police as he crossed from Maryland to Pennsylvania. His first call was picked up by Maryland authorities, but was dropped, possibly because he had crossed state lines, according to police officials. He then made a second call that was picked up by the Pennsylvania State Police.
"This was a very extreme case, this was a rarity. And frankly the details of the case are disturbing," Pennsylvania State Police Trooper Adam Reed said.
The FBI has joined the investigation as the search for the killer intensifies, with authorities looking for the driver of a dark pick-up truck.
Pennsylvania State Police Capt. Steven Junkin said the assailant is believed to have been a man in a dark-colored Ford Ranger XLT pickup truck, a model that has not been made in a decade.
Junkin said it likely that there is damage to the front door of the truck.
"This actor had murderous intent," Junkin said, surrounded by other members of a task force set up to investigate the crime. "We obviously have an individual who was so incensed that he continued to pursue Mr. Davison."
Davison was traveling along Interstate 81 in Pennsylvania after visiting family for the holidays. Just after 2 a.m., Davison made a frantic call to police, telling a dispatcher that a Ford Ranger-style pickup truck was trying to run him off the road.
The other vehicle then rammed Davison's car, forcing him on to the snowy median, where his car became stranded, according to police. That's when police say the driver of the truck got out of the vehicle and fired several shots. Davison was hit several times and later died from his injuries at a local hospital.
"He was on 911 for the majority of this incident and we are reviewing the tapes to try and see if we can get any information to help us find out what happened," State Trooper Robert Hicks said.
Police said they are concerned that this wasn't an isolated incident because seven hours before Davison was shot, a black truck pulled up alongside another car in nearby Monaghan Township, Pa., and someone inside fired several shots, narrowly missing the driver's head.
Authorities are investigating whether the two incidents are related.
"We're taking this incident very seriously. We're leaving no stone unturned as far as the investigation is concerned," Hicks said.
The Associated Press contributed to this article.