A Farmington man was arrested Friday and charged with killing his infant son 38 years ago in Brunswick, making it the oldest unsolved homicide case in which Maine State Police have brought charges.

The arrest of Burton “Ben” Hagar, 62, followed an indictment on the charges by a Cumberland County Grand Jury, according to a news release Friday from Steve McCausland, spokesman for the Department of Public Safety. Hagar was arrested just before noon Friday at his home on Marvel Street in Farmington by Maine State Police detectives and taken to the Franklin County Jail in Farmington.

Hagar was expected to make his first appearance in Cumberland County Superior Court in Portland at 1 p.m. Wednesday, McCausland said.

Hagar’s 4-month-old son, Nathan Hagar, was found unresponsive in the family’s 16 School St. apartment in Brunswick and died later at Parkview Hospital in Brunswick on May 9, 1979.

McCausland said the baby’s death originally was investigated as a SIDS case — sudden infant death syndrome — but Maine State Police detectives “reopened the case quietly” in 1991. During the past year, police detectives “gathered new information about the death and coordinated the investigation with the new Unsolved Homicide Unit, which led to the Attorney General’s Office presenting the case to the grand jury this week,” McCausland said.

In an interview, McCausland refused to comment further on what led police to reopen the case, saying any further information would come out in court.

Hagar’s lone prior criminal conviction predated his son’s death. In 1977, Hagar was convicted on two counts of possession of stolen property, a misdemeanor, and he was fined $250, according to a statewide criminal records check.

Col. Robert Williams, chief of the Maine State Police, praised the new investigative unit for bringing charges in its first case.

“There are more than 100 Maine unsolved homicides and the new unit is reviewing each case,” Williams said in the release. “The hard work of this dedicated group from Maine State Police and the Attorney General’s Office have brought this first unsolved homicide to this point, and there will be other success stories as their work continues.”

The Unsolved Homicide Unit was formed in 2014 by the state’s 126th Legislature but did not receive funding until the following year. It has been fully staffed since Februrary 2016, McCausland said. The unit is made up of two veteran Maine State Police detectives with experience in cold case investigation as well as a staffer with the state crime lab.

“The beauty about this new unsolved unit is they’re working exclusively on unsolved homicides and their work is augmented by all the work prior that has been done by these individual detectives who have worked on the cases over the years,” McCausland said.

Assistant Attorney General Lara Nomani helps develop the unit’s legal cases while Renee Ordway, the victim witness advocate, works as a liaison between survivor families and the cold case unit, said Timothy Feeley, spokesman for the attorney general’s office.

Until Hagar’s arrest, the oldest case state police had cracked resulted in the arrest of Gary Raub in 2012 for an Augusta homicide that took place in 1976 — 36 years earlier. Raub was convicted of killing Blanche M. Kimball, of Augusta, in 1976 and sentenced to 20 years in prison. Raub died last year at PenBay Medical Center in Rockport after serving about two years of his sentence.