The father of a Salem man accused of killing two Oregon law enforcement officers in a bank explosion was arrested Tuesday on bomb-making conspiracy charges, authorities said.

Bruce Turnidge, 57, faces charges of conspiracy to manufacture and possess an explosive device, the Marion County district attorney's office said.

His son, 32-year-old Joshua Turnidge, appeared in court Tuesday on charges that include aggravated murder in the explosion Friday at the West Coast Bank in the agricultural town of Woodburn. The charge carries a potential death penalty.

"My client is clear-headed," said Joshua Turnidge's court-appointed attorney, Steven Krasik of Salem. "He was surprised to be arrested. And he is optimistic that he will be cleared of all these charges."

Click here for photos.

Officers arrested his father at a farm about 13 miles southwest of Salem, the city where Joshua lives. Lt. Sheila Lorance of the Marion County Sheriff's Office said law enforcers were searching all 750 acres of the farm "from front to back." She would not elaborate.

Bruce Turnidge does not own the farm, but public records list it as his address. It was not clear whether he was a renter there, and the owner was not immediately available for comment.

The blast killed a State Police bomb technician, Senior Trooper William Hakim, and a Woodburn officer, Capt. Tom Tennant. It critically injured Woodburn Police Chief Scott Russell; a probable cause statement said Russell lost his right leg from the knee down and his left leg was mutilated.

The probable cause statement said that on Friday morning, a man called in a bomb threat to the Wells Fargo Bank in Woodburn, which is next door to the West Coast Bank branch.

The man said "if 'they' didn't leave the building, all of them would die," the court document states.

The man also said that a cell phone would be found next to a garbage can, and that he would give further instructions on it. The man also said he would be calling the West Coast Bank.

Local police officers arrived at the Wells Fargo building, opened a garbage bin and spotted a cell phone on top of what appeared to be a package. Hakim and an FBI bomb technician were called. They examined the package and cell phone and determined the package was a hoax device.

Woodburn police searched the area around the two banks for other devices, and a green metal box was spotted next to the West Coast Bank building.

Hakim, Tennant and Russell arrived at the West Coast Bank. After Hakim inspected and X-rayed the green box, he said he was "confident that it was a hoax device and that it could be taken apart to be placed into evidence."

The statement says a bank employee saw Hakim trying to open the box while Tennant held it when the bomb exploded. The bank employee was treated at a hospital and released.

Joshua Turnidge, a Navy veteran who worked in a biodiesel fuel enterprise with his uncle, appeared in court Tuesday morning for the first time since his Sunday arrest. He was appointed the attorney and did not enter a plea. His next scheduled court date is Dec. 26.

Authorities have refused to say what they think the motive was for the bombing.

The court document says Turnidge was seen on a store's surveillance video walking to his father's pickup truck after buying air time for the cell phone that was found at the Wells Fargo branch. The airtime was purchased a day before the bombing.

The father-and-son duo have a record of traffic and vehicle law violations, but no record of serious offenses in Oregon.