A gunman opened fire aboard a packed Greyhound bus as it was traveling from Los Angeles to San Francisco early Monday, killing one passenger and wounding five others before the driver pulled over onto the shoulder and managed to force the killer off, authorities said.

The suspect was taken into custody without incident, and the motive was not immediately known, said California Highway Patrol Sgt. Brian Pennings.

Passenger Mark Grabban, 29, told NBC News the gunman was talking “incoherently” when he boarded the bus and had argued with someone who had asked him to be quiet.

“He was muttering things, about ‘Wait till we get to the station,’” Grabban said.

The dead passenger was identified as a 51-year-old woman from Colombia. Two victims were hospitalized with serious injuries, Pennings said.

The shooting took place shortly before 1:30 a.m. in the small community of Lebec, about 70 miles (113 kilometers) northwest of Los Angeles, as the bus was traveling along a mountainous stretch of Interstate 5 with 43 people aboard, authorities said.

Grabban said he heard the gunman — a tall, massive figure, he recalled — curse and cock his gun, firing eight or nine shots. The driver initially thought the gunshots were the sound of an engine problem, the passenger said.

“I dove to the floor right to under the seat. I got to my girlfriend, tried to put her head down,” Grabban said, adding that the shooter aimed toward the back of the bus where he was sitting. “I was just waiting for the next shot. I was assuming I was going to get shot.”

A casing ended up on Grabban’s lap, he said.

“I saw the blood on the floor of the aisle,” Grabban said. I looked to the woman on the left, and she wasn’t responding, wasn’t moving or anything. She was lifeless.”

Pennings said the driver “immediately pulled to the right shoulder and somehow — we’re still trying to figure out to how this happened — were able to coerce the suspect off of the bus,”

After leaving the gunman behind, the driver continued on to the next exit and pulled into a gas station parking lot. “His actions were very appropriate and one could say heroic,” the officer said.

Highway patrol officers found the suspect a few minutes later. A handgun believed to have been used in the shooting had been left on the bus, Pennings said.

The names of the suspect and the victims were not immediately released.

The shooting happened when the bus was at the top of Tejon Pass, which rises to an elevation of more than 4,100 feet (1,250 meters) in Lebec.

Greyhound prohibits passengers from bringing guns, explosives or dangerous chemicals on board its buses or in their luggage, according to its website. The company declined to answer additional questions about security on its buses.

(AP)