Updated

A Kansas sheriff said Saturday that investigators have no idea why a man "came out of nowhere" and fatally shot a veteran police officer in the head before killing himself.

Atchison Sgt. David Enzbrenner had gone to a house Friday afternoon to serve a nuisance order when Skyler Barbee approached the officer and shot him, said Atchison County Sheriff John Calhoon. Enzbrenner, 46, an Atchison officer for 24 years, was flown to an area hospital where he was pronounced dead.

Barbee, 25, who turned the gun on himself after shooting the officer, died at the scene, the sheriff said.

"It's been a rough day," Calhoon told The Associated Press on Saturday. "I've had to look at many officers grieve today. I've done so myself. It's something I hope I never have to go through again in my career. In my 26 years, this probably hurts more than anything I've seen."

Calhoon's office, the Kansas Highway Patrol and eight to 10 other agencies from Kansas and Missouri were providing law enforcement to Atchison on Saturday in the wake of the shooting. The sheriff said his office and Atchison police have a close relationship and he wants to do what he can to give Enzbrenner's colleagues in the northeast Kansas community of about 10,500 along the Missouri River time to grieve.

"The Atchison Police Department is immediate family, and all of us are extended family to them," Calhoon said. "We owe it to them."

A candlelight vigil was planned for Saturday night.

Enzbrenner was married and the father of three girls. The sheriff said the officer's death, which came less than six weeks after an Atchison grain bin explosion killed six people, has taken a tremendous toll on the community a half-hour southeast of St. Joseph Mo.

"We're going to get through it," Calhoon said.

He said it doesn't appear that Barbee was connected to the home where Enzbrenner arrived just before 4 p.m. Friday to serve the nuisance order.

"We don't have any idea at this point why he did it," the sheriff said, pointing out that Barbee was "not a relative, not the occupant."

Barbee was arrested by Atchison police in August on charges of vehicle burglary, battery on a law enforcement officer and obstruction of the legal process.

Atchison County prosecutor Jerry Kuckelman told the St. Joseph News-Press in Missouri that Barbee was sentenced in August to 45 days in jail for battery on a law enforcement officer and had served that time. Kuckelman's office did not immediately return a phone call to the AP for comment Saturday.

Kansas Highway Patrol spokesman Don Hughes said multi-agency operations like the one in Atchison to relieve grieving law enforcement employees is standard procedure when an officer is killed.

"When this happens, especially if it has happened before in your agency, you know what they're going through and what they're going to need," he said. "It's part of that law enforcement brotherhood that brings us together."

Officers with the various agencies are taking calls, patrolling streets and performing the same jobs they would in their own jurisdictions, Hughes said.

"We're going to be here as long as we need to be here," he said.