"A former employee of PSE[&]G, whom authorities identified as Gary T. Curtis, age 58, Washington, New Jersey approached Mr. Heller in the parking lot, shooting him outside of his vehicle," the Somerset Prosecutor's Office said in a statement.
Heller was found on Thursday morning when Franklin Township Police responded to multiple 9-1-1 calls reporting a shooting victim within the parking lot of PSE&G utility company.
Detectives tracked down Curtis, the alleged assailant, in a vehicle in Bridgewater Township, New Jersey where he died while suffering from a self-inflicted gunshot wound, according to the release.
The homicide investigation remains on-going to determine motive, the release added.
Heller, a Republican, was elected to the Milford Borough Council in 2017 and again in 2020.
A week ago, Eunice Dwumfour, a Republican council member, who represented Sayreville, was found fatally shot in her vehicle near her home. Police have not identified a suspect or determined a motive in her death. Sayreville is about 55 miles east of Milford.
Authorities are probing if there are any connections between the two deaths but officials in the prosecutor's office have said Heller's death appears to be an isolated incident.
PSE&G said Heller worked with the company for 11 years as a senior distribution supervisor.