Christopher W. Snyder killed 3 people at a neighbor’s house and then himself last week in Maryland. (Obtained by The Washington Post)

Christopher W. Snyder, the federally licensed gun dealer who fatally shot three people in a neighbor’s house in suburban Maryland last week, was investigated by police in 2014 after his then-girlfriend told police he had placed a pistol to her head and threatened to kill her, according to four law enforcement officials with direct knowledge of the incident.

Montgomery County investigators in the 2014 event learned that Snyder had more than 60 guns registered to him in his home, most military-style rifles, according to the officials. They staked out his home, followed him as he drove and pulled him over, and he was charged with first-degree assault, using a gun in a felony and reckless endangerment.

County prosecutors dropped the case, according to the officials, because the accusing woman later said she would not testify against Snyder. Efforts to reach her over the past several days — by phone and via Facebook — were unsuccessful.

Montgomery County Police Chief J. Thomas Manger confirmed Monday night that his investigators had charged Snyder in the 2014 domestic violence case. After the case was dropped, Snyder sent emails to Manger, complaining that detectives had treated him unfairly and should not have believed his girlfriend.

Manger said Monday that he and others in his department looked into Snyder’s complaints at the time and found them to be without merit.

“There was a real arrogant tone to his emails,” Manger recalled. “He was obsessed about this.”

The old case came into play indirectly last week when police knew to be wary of a weapons cache after being called on May 7 to the cul-de-sac where Snyder was staying with his wife. She had run to a neighbor’s house seeking help, claiming Snyder had been holding her captive over the weekend after an argument.

Snyder, 41, pursued her into the home and shot and killed a neighbor, a visitor and a workman, who by later accounts had tried to help his wife. She and two others escaped uninjured in the rampage in the community of Brookeville.

Snyder then holed up in his residence, where police SWAT teams took positions around his house and negotiators tried for hours by phone to persuade Snyder to surrender. He eventually shot and killed himself inside.

The public record of the 2014 case was stripped after Snyder petitioned the Montgomery District Court to have the case expunged, according to law enforcement officials who spoke on the condition of anonymity to be able to describe events from that incident.

In other dealings with the courts, Snyder also sought to have filings sealed from public view, court records show.

During a 2017 divorce case in Howard County, Snyder successfully petitioned the court to have certain personal information — including his address, phone number and financial statements — placed under shield. He told the court it could jeopardize what he described as his security clearances.

Jeremy Eldridge, a lawyer who represented Snyder in Howard County, could not be immediately reached for comment Monday.

Snyder also appears to have had a criminal case in 2017 expunged in Montgomery.

In that matter, police charged him with possession of a dangerous weapon and possession of unspecified drugs, according to LexisNexis, a database that logs court records as they become public.

Detailed records on the 2017 case, including the alleged weapon and type of drug, are no longer available at the Montgomery District Courthouse or in Maryland Case Search, the state’s online listing of court records.

It is the description of the 2014 case, however, that relates to some elements of Snyder’s final act involving guns and threats.

In August 2014, his ­then-girlfriend went to police and accused him of pulling a handgun from his waistband, placing it against her head, and saying he was going to kill her and himself, according to three of the officials who spoke about the incident. Snyder told her the shooting would be painless and everything would go dark, they said.

“I want you to come with me,” Snyder allegedly told his girlfriend, according to two of the officials. “Would you do that for me and come with me?”

In Maryland, expungements are fairly common. In many instances, they allow people who have made a minor mistake or had criminal charges dismissed to move on in their lives without a lingering cloud of suspicion.

Jennifer Jenkins contributed to this report.