CONCORD, N.H. — An apparent murder-suicide. A beloved police chief gunned down by a man who later turned the gun on his on-again-off-again girlfriend and himself. A man shot dead on a dirt road.

In just 72 hours, the number of homicides in New Hampshire this year doubled from four to eight.

The bloodshed began Thursday afternoon with two men dead in Dalton, followed hours later by the slaying of a veteran Greenland police chief just days away from retirement and by Saturday reached Chesterfield, where a man was killed on a dirt road.

In a small state accustomed to between 15 and 19 homicides a year, it was three days of seemingly nonstop violence. The wave of shootings has alarmed residents in small towns unaccustomed to violent crime and sent investigators streaming from one scene to the next.

Professor Mark Fischler, chairman of the criminal justice department at Plymouth State University, said the streak of shootings is shocking in a state the size of New Hampshire.

“I consider ourselves one big family,” Fischler said. “It’s incredibly sad to see such little value for human life.”

Killed in Dalton were 48-year-old Joseph Besk and 45-year-old Christopher Smith, the apparent gunman. Smith’s death has been ruled a suicide. A third man, 54-year-old Wayne Ainsworth, is recovering from gunshot wounds.

Besk and Ainsworth were both convicted sex offenders who were married behind bars just weeks after the state’s same-sex marriage law took effect in January 2010. Smith apparently lived with them, but the motive for the shootings is not clear.

“To have this happen in a small community like ours is an eye-opener,” said Mario Audit, the police chief in Dalton, population 900. “It’s usually pretty peaceful. In Greenland, they realize that, too.”

Audit — one of four officers in the northern New Hampshire town — hopes to know more when state police investigators return. “We’re waiting for Greenland to settle out,” he said.

The investigation in Dalton was abruptly eclipsed when word of the Greenland shootings came shortly after 6:30 p.m. Thursday. Five officers were shot, the extent of their injuries unclear, according to early reports. Crime scene investigators and trucks were redeployed.

Greenland’s police chief of 12 years — Michael Maloney — was confirmed dead. He was shot in the head while trying to serve a search warrant on 29-year-old Cullen Mutrie, a man with an arrest record for domestic abuse and possession of steroids, court records show. Four detectives affiliated with the attorney general’s drug task force were shot as well.

Maloney, 48, was a week away from retirement after a quarter-century in law enforcement. He was looking forward to spending more time with his family.

The wounded officers are detective Gregory Turner, 32, a six-year veteran of the Dover police department, who was treated for a gunshot wound to the shoulder and released; detective Eric Kulberg, 31, a seven-year veteran of the University of New Hampshire police department, who was treated for a gunshot wound to the arm and released; detective Scott Kukesh, 33, a 10-year veteran of the Newmarket police department and detective Jeremiah Murphy, 34, a seven-year veteran of the Rochester police department, both of whom remain hospitalized in stable condition.

After a tense, overnight standoff, Mutrie was found dead in the home along with 26-year-old Brittany Tibbetts of Berwick, Maine. Family members said Tibbetts was a former girlfriend of Mutrie who returned to him recently to help him work out issues that were upsetting him. Authorities have ruled her death a homicide and his a suicide.

As the state was still reeling from Maloney’s death, investigators Saturday were called to yet another fatal shooting in Chesterfield — a town of about 3,600 people near Brattleboro, Vt. They found one man dead on a dirt road and another injured from gunshot wounds. Their identities have yet to be released, although prosecutors confirm the death is a homicide.

Senior Assistant Attorney General Jane Young, head of the criminal division, said the string of shootings in such a compact timeframe brings to mind the fatal shootings of three people in a North Conway store on July 2, 2007. That same day in Manchester, a man shot to death his 62-year-old girlfriend, then killed himself.

“For a small state, there’s a fair amount of territory to have to cover,” Young said.