An anti-Trump activist has been accused of executing his neighbor who was a prominent Republican supporter.

Clayton Carter allegedly shot George Jennings, both 51, twice in the head outside his home in Pennsylvania in the early hours of August 8.

The men had already been arguing the previous night and police were called after Carter pulled a gun, but managed to diffuse the situation.

Clayton Carter, 51 (left), is accused of shooting neighbor George Jennings, also 51 (right), twice in the head outside his home in Pennsylvania last week

However, officers were called back just a few hours later to reports of a fatal attack, ABC 6 News reports.

The pair had been feuding for some time, neighbors said, adding that they were afraid of Carter's unpredictable nature.

ABC reports that his yard was covered with hand-painted anti-Trump signs and was often filled with cars.

Jennings, meanwhile, was a member of the Chester County Republican Committee, though it is not thought their beliefs were directly responsible for the shooting.

Investigators were first called to the address around 8pm on August 7 because the two men were fighting about cursing and video recording in a back yard.

Officers resolved that dispute, but at 1am on August 8 they were called back to another argument, this time involving lights.

Jennings was a prominent Republican supporter while Carter had a lawn littered with anti-Trump signs (pictured). Neighbors said the men had been involved in a long-running dispute but the shooting was not directly related to their political beliefs

Carter accused Jennings of shining a light into his eyes as he was returning home, and went inside to fetch a .380-caliber Ruger semi-automatic handgun.

Carter went back outside and parked his car up on Jennings' lawn with his lights on full beam, according to a criminal complaint seen by Philly.com.

A heated argument then started and Carter shot Jennings in the head, knocking him to the ground, the complaint says.

Carter then shot Jennings in the head a second time while standing over his body, as his distraught wife watched from inside the house, it is alleged.

Carter admitted shooting Jennings but says he acted in self defense after Jennings advanced on him with a knife.

Police say they recovered two shell casings from the scene - one from Carter's yard, and one from beside Jennings' body.

They also recovered a knife, though it is not clear where the weapon was found.