MIDLAND CITY — Police SWAT teams and hostage negotiators were locked in a standoff today with a gunman authorities say intercepted a school bus, killed the driver, snatched a kindergartener and retreated into a bunker at his home.

Neighbors described the gunman as a paranoid and combative man who once beat a dog to death with a lead pipe, threatened to shoot children for setting foot on his property and patrolled his yard at night with a flashlight and a shotgun.

The gunman, identified by neighbors as Jimmy Lee Dykes, a 65-year-old retired truck driver, was supposed to appear in court today to answer charges he shot at his neighbors in a dispute over a speed bump.

The standoff dragged on through the night and into the afternoon today after the gunman boarded a stopped school bus in the small town of Midland City on Tuesday afternoon, authorities said. The town is in the southeast corner of Alabama.

Sheriff Wally Olsen said the man shot the driver when he refused to let a 6-year-old child off the bus. The gunman then took the boy away.

The bus driver, Charles Albert Poland, Jr., 66, was hailed by School Superintendent Donny Bynum as a hero who gave his life to protect 21 students.

About 50 vehicles from federal, state and local agencies were clustered Wednesday at the end of a dirt road near Dykes' home. Authorities gave no details on the standoff, and it was not immediately clear whether they had made contact with Dykes or he had made any demands.

Homes nearby were evacuated early in the morning after authorities found what was believed to be a bomb on his property.

County Coroner Woodrow Hilboldt said Dykes was believed to be holed up in an underground bunker of the sort used to take shelter from a tornado.

Mike and Patricia Smith, who live across the street from Dykes and whose two children were on the bus when the shooting happened, said their youngsters had a run-in with him about 10 months ago.

"My bulldogs got loose and went over there," Patricia Smith said. "The children went to get them. He threatened to shoot them if they came back."

"He's very paranoid," her husband said. "He goes around in his yard at night with a flashlight and shotgun."

"Everybody up the hill tried to avoid him," he said.

Patricia Smith said her children told her what happened on the bus: Two other children had just been dropped off and the Smith children were next. Dykes stepped onto the bus and grabbed the door so the driver couldn't close it. Dykes told the driver he wanted two boys, 6 to 8 years old, without saying why.

According to Smith, Dykes started to step into the aisle of the bus and the driver put his arm out to block him. Dykes fired four shots at Poland with a handgun, Smith said.

"He did give his life, saving children," Mike Smith said.

Patricia Smith said her daughter, a high school senior, began corralling the other children and headed for the back of the bus while Dykes and the driver were arguing. Later, Smith's son ran inside his house. "He said 'the crazy man' across the street shot the bus driver and Mr. Poland won't wake up," Patricia Smith said.

Patricia Smith ran over to the bus and saw the driver slumped over in his seat. Her daughter used another child's cellphone to call 911.

Court records showed Dykes had been scheduled to appear in court this morning to face a charge of menacing some neighbors as they drove by his house last month.

Claudia Davis said he yelled and fired shots at her, her son and her baby grandson over damage Dykes claimed their pickup truck did to a makeshift speed bump in the dirt road. No one was hurt.

"Before this happened I would see him at several places and he would just stare a hole through me," Davis said. "On Monday I saw him at a laundromat and he seen me when I was getting in my truck, and he just stared and stared and stared at me."