SALEM (AP) - The investigation into a bombing that killed two Oregon law enforcement officers at a Woodburn bank has narrowed to a father-son tandem.

Two days after police arrested Joshua Turnidge, officers went to a farm in the Talbot area of southwest Marion County and took the man's father, 57-year-old Bruce Turnidge, into custody. Members of Linn County Search and Rescue were soon walking shoulder-to-shoulder in the farm's fields, looking for evidence.

Officials have yet to describe what specific actions the father allegedly 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, Marion County deputy district attorney. Those charges include murder, attempted murder, assault and the manufacture and possession of a destructive device.

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 elder Turnidge is scheduled to be arraigned Thursday morning.