Updated

Sheriff's deputies discovered the truck of a man suspected of fatally shooting his wife and two young daughters at their rural Northern California home, but he's armed and dangerous and still on the loose, authorities said.

Humboldt County Sheriff's officials received 911 calls late Wednesday afternoon reporting that Shane Franklin Miller, 45, was driving the truck in a rural area near Petrolia, Lt. Steve Knight said. Deputies found the truck after converging on the area, but Miller wasn't there.

Petrolia is about 200 miles west of the site of the slayings in the Shasta County community of Shingletown. Shingletown is about 230 miles northeast of San Francisco.

"There is a manhunt for him right now," Shasta County Sheriff's Lt. Dave Kent said earlier Wednesday. "He's a prime suspect. We're not looking for anybody else."

Miller is believed to be heavily armed and extremely dangerous, authorities said. He has been in trouble with the law before.

In 2002, Miller was charged in San Francisco with making and selling marijuana for distribution, being a felon in possession of a firearm, possessing a machine gun and money laundering, according to court records. He pleaded guilty to being a felon in possession of a gun and was sentenced to three years and 10 months in prison. He was released in May 2007, according to the federal Bureau of Prisons.

Kent said Shasta County Sheriff's deputies received a call from Miller's house around 7:45 p.m. Tuesday. When they arrived, they found the bodies of Miller's wife, Sandy, 34, and two daughters, Shelby, 8, and Shasta, 4.

All three had been shot multiple times, Kent said.

Kent said investigators had not determined who placed the call, but he said it was from one of the victims as the shooting was in progress.

Authorities have not recovered the gun, or guns, believed to have been used in the shooting, but Kent said more weapons were found in the house.

"We found several different types of weapons, ammunition in the house, so he may be heavily fortified at this time," Kent told The Associated Press.

Miller may be heading to a cabin in coastal Humboldt County, where authorities have said several weapons may be stored.

Initially, authorities believed the cabin was in Ferndale. But Kent said Wednesday evening he could not confirm the location, and Ferndale Police Chief Bret Smith said there was a residence in nearby Petrolia, not Ferndale, where Miller has stayed in the past.

The two-story house where the shooting took place is nestled among pine trees, with a detached garage and shed in the back. The Redding Searchlight reported that horses and llamas graze on the property.

Investigators had not determined a motive for the shooting, but Kent noted deputies had gone to the home last month on a domestic dispute call.

Schools in the rural community of about 2,000 people were locked down during the day Wednesday, and a forest harvest demonstration for local schools set for Wednesday and Thursday was rescheduled for next week.

Miller's two daughters both attended school in the Black Butte Union Elementary School District, superintendent Don Aust told The Record Searchlight.

The girls' parents pulled Shelby out of the elementary school and Shasta out of the preschool programs around three to four weeks ago, Aust said.