A Pennsylvania man in prison for killing his wife and stepdaughter in March has been charged with another slaying, this time of a man who witnessed a burglary he committed in 1988, and investigators say he’s a suspect in at least six more murders.

Regis Andrew Brown, 59, has been charged with criminal homicide in the shooting death of Bryce Kenneth Tompkins, 45, whose body was found by hunters the day after Christmas, partially submerged in a creek near New Castle. He is also charged with two counts of aggravated assault and a single count of witness intimidation.

WPXI in Pittsburgh reported that police officials said Brown admitted his involvement in the slaying, telling cold case investigators he shot Tompkins, a neighbor, because he had witnessed a burglary Brown and another man, Paul Michael Ayersman, committed in New Castle. Ayersman is now dead.

Pennsylvania State Trooper Joe Vascetti said during a news conference Thursday that Brown is also suspected in a string of homicides in the southwestern portion of the state between 1986 and 2016.

“He’s either been arrested for or confessed to or is a strong suspect in eight homicides right now,” Vascetti said. “We’ve done extensive interviews with him. He was in or around Lawrence County back in the late ‘70s and early ‘80s. He associated with a lot of individuals that we are looking at that are involved in some other homicides back in that era. He may be tied to or have knowledge (of) an additional six to eight homicides from that area.”

If that is the case, Brown could be tied in one way or another to as many as 16 slayings.

See the news conference on Brown’s latest arrest below.

Vascetti declined to go into further detail about those cases because they are ongoing investigations. He said Brown confessed to at least two additional homicides besides that of Tompkins.

“He has a checkered past,” Vascetti said. “He is a violent offender. He was involved in a lot of violent crimes back then.”

Lawrence County District Attorney Joshua Lamancusa said during the news conference that Brown and Ayersman were arrested in December 1988 for a series of burglaries they'd committed in New Castle. Taken in one of those burglaries was a .38-caliber Smith & Wesson revolver -- the same caliber of the gun that was used to kill Tompkins.

Tompkins was shot twice in the back, Lamancusa said.

Lamancusa said that detectives questioned Brown about the Tompkins slaying March 19, shortly after Brown had been arrested in connection with the deaths of his wife and stepdaughter. According to Erie News Now, Michele Brown, 53, was bludgeoned to death and her daughter, Tammy Greenawalt, 35, was stabbed to death.

“It was a horrendous scene,” Vascetti said Thursday. “He’s just a vicious individual.”

The New York Post reported that Brown tied Greenawalt to a chair before beginning to stab her. He beat his wife to death in their garage when she returned home later that day.

Greenawalt's 14-year-old daughter witnessed portions of the killings before her grandfather tied her up in a bedroom of his Fairview Township home for most of the weekend, Erie News Now reported. When she went to school the following Monday, school staff noticed marks on her wrists and the girl admitted her grandfather had tied her up.

Police officers who went to the Brown home for a welfare check when neither woman showed up for work found Michele Brown's body wrapped in a rug in the garage. Greenawalt was still seated in the chair and covered with a blanket, the news station reported.

Officers found a sledgehammer and a broken pair of scissors, both of which appeared to have blood on them, the station said.

Regis Brown, who pleaded guilty to the murders last month, was sentenced to life in prison.

Lamancusa said Brown confessed to killing Tompkins during that interview in March.

“He described where the killing occurred, the motive for it, the disposal of the body and the subsequent burial of the .38-caliber pistol,” Lamancusa said.

The district attorney said that investigators tried on two separate occasions to find the buried weapon but could not because the area had been built up in the intervening years with dirt and fill.

“However, several witnesses have been developed in this case throughout the entire investigation and are prepared to testify to their knowledge of the killing,” he said.

Those witnesses’ identities are being kept secret due to Brown’s affiliation with at least one motorcycle gang, Lamancusa said.

Regis Brown's page on the Pennsylvania Department of Corrections website is pictured. Brown, who is already serving a life sentence in the March murders of his wife, Michele Brown, and adult stepdaughter, Tammy Greenawalt, has been charged with criminal homicide in the shooting death of Bryce Kenneth Tompkins, 45, whose body was found by hunters the day after Christmas 1988. Brown, 59, is also suspected in up to eight additional slayings.

Credit: Pennsylvania Department of Corrections

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Credit: Pennsylvania Department of Corrections

Vascetti said Brown was a person of interest in Tompkins’ slaying from the beginning, specifically because of the burglary spree he and Ayersman committed. When Brown was arrested, he was in possession of a 12-gauge Mossberg shotgun stolen in the same burglary in which the .38-caliber revolver was taken.

“(Troopers) knew it was from a burglary near where the victim lived and knew Regis Brown lived two doors up from the victim, and, you know, things started to click,” Vascetti said.

He said Brown did not know Tompkins, who had a habit of walking around the neighborhood at night.

“Unfortunately, he was in the wrong place at the wrong time,” Vascetti said.

The men confronted him a few nights later and shot him execution-style, the trooper said.

“Just a brutal murder,” Vascetti said. “Ruthless.”

Tompkins’ family expressed relief that the case has finally been solved.

"After 30 years, I'm completely relieved for our family that we can have this closure and my dad can rest now," his daughter, Stacey Harding, said, according to WPXI.

Brown's stepson, Alan Greenawalt, said he wishes the arrest had come much sooner. If it had, he told Erie News Now, his mother and sister might still be alive.

"I just wish things were different," Greenawalt said. "Whatever he gets, he gets. He deserves it."