"I can tell you the courage that was demonstrated by Mr. Krumm was absolutely without equal," he said, adding that the father's actions could offer some measure of comfort to those affected by the killings.
He said police still were trying to figure out what motivated Christopher Krumm to attack his father and girlfriend, Heidi Arnold, 42, a math instructor at the college. Arnold was found stabbed to death in front of the home she shared with James Krumm.
After shooting his father with the arrow, the son stabbed himself, then fatally stabbed his father in the chest in a struggle in the classroom, Walsh said.
Police arrived to find James Krumm dead and Christopher Krumm barely alive; the younger Krumm died soon after students fled in a panic. Authorities locked down the campus for two hours.
Police began getting reports about the attack on Arnold soon after they responded by the dozen to the campus attack.
Walsh said Krumm also had two knives with him and the knife used was "very large."
"It's one of those situations you don't think is going to come home. It's not going to happen here," Walsh said.
Arnold died of multiple stab wounds. Her body was found in the gutter of her street. Evidence suggested much of the attack occurred outside the home.
Christopher Krumm had recently driven to Casper from Connecticut and had been staying at a hotel. He had no significant history of encounters with police.
Police were uncertain what went awry in his relationship with his father.
The building where the attack happened remained cordoned off by police tape. A security guard let students back in, one at a time, to retrieve belongings.
Andra Charter, a sophomore, emerged with a coffee mug. She recalled hearing screams outside her biology class before getting word about what had happened.
"As we were walking out, there was a girl screaming, 'There's somebody stabbing Mr. Krumm!' " Charter said.
No students were hurt in the attack.