A “quiet guy” from Long Island barricaded himself inside of his home on Tuesday — sparking a four-hour standoff with police, which ended with cops busting down his door and finding his wife shot to death, officials said.

Robert Brown, 65, is facing a second-degree murder charge for the alleged killing, according to Suffolk County Police.

He was at his home on Doris Avenue in Riverhead when authorities got reports of him walking around the residence, carrying a handgun. Responding officers arrived around 9:20 a.m. to find the senior-citizen barricaded inside.

“Mr. Brown we need you to come to the front door,” police told him over a loudspeaker, according to RiverheadLOCAL. “We need to know the status of your wife.”

After a nearly four-hour standoff, cops said they “knocked down the front door of the house” and took Brown into custody. His wife, Sarah Brown, 71, was already dead from a gunshot wound when officers found her. It’s unclear if she was killed before or after police arrived on scene.

Suffolk County Police Hostage Negotiation Team and Emergency Service Section officers had responded to the house and tried getting Brown to come outside, officials said.

Upon his arrest, authorities took him to Suffolk County Police Headquarters in Yaphank and then the Riverhead Town Police Headquarters to be held overnight. He was scheduled to be arraigned on Wednesday at the Town of Riverhead Justice Court.

Neighbors who spoke to the Riverhead News-Review and other local outlets described Brown as a “pillar of the community.”

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“He’s a nice person,” said one woman, speaking to RiverheadLOCAL. “I don’t know what happened. He’s a very quiet guy, pleasant, always encouraging other people. When they’d go fishing they always brought my mother some fish.”

Another resident said, “This is not like Bobby. There has to be some kind of mental issue.”