SALEM (AP) — Investigators are pointing to a father and son as the key suspects in a bombing that killed two Oregon law enforcement officers at a Woodburn bank.

Two days after police arrested Joshua Turnidge, officers went to a farm in the rural community of Jefferson and took the man’s father, 57-year-old Bruce Turnidge, into custody Tuesday.

Officials have yet to describe what specific actions they believe father carried out in Friday’s bombing of a Woodburn bank, but said late Tuesday his role wasn’t minor.

“There was sufficient evidence for him to be charged with all the same offenses as his son,” said Courtland Geyer, the deputy district attorney in Marion County. Those charges include murder, attempted murder, assault and the manufacture and possession of a destructive device.

He’s scheduled to be arraigned Thursday morning.

Within hours of his arrest, officers were soon walking shoulder-to-shoulder in the farm’s cabbage fields, looking for evidence.

Geyer declined to reveal what authorities think motivated the men to build a bomb and place it outside a branch of West Coast Bank. Documents released Tuesday as part of Joshua Turnidge’s arraignment described what happened, but not why.

Joshua Turnidge, 32, did not enter a plea Tuesday and showed little emotion when hearing the charges that carry a potential death penalty.

“My client is clear-headed,” said 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.”

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.

The court document said Joshua Turnidge was seen on a store’s surveillance video walking to his father’s pickup 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.

The Turnidges come from a family with strong roots in the Willamette Valley. Decades ago, the family helped start the Salem Academy Christian schools.

“His dad had the biggest peppermint farm in the whole Willamette Valley,” said Dale Turnidge, 88, of Salem, a cousin of Bruce Turnidge’s father. “Turnidge and peppermint was synonymous.”

When Bruce Turnidge was about 18, his father lost the farm, leaving the young man and his brothers to set out on their own, Dale Turnidge said.

He said Bruce’s older brother, Pat Turnidge, got involved in local politics, while another brother, Doug Turnidge, became director of an Oregon youth camp. He said Bruce ran a backhoe business for awhile, then drifted between farms in Oregon and Nevada. He does not own the farm where he was arrested.

Vance Day, the chairman of the Oregon Republican Party, said he has known Bruce and Pat Turnidge for several years and would be “very surprised” if Bruce were involved in the bombing.

“I know him to be strong, very pro-American,” he said. “He doesn’t believe in violence of that sort whatsoever.”