Davis, who appears to have been a random victim, remains in "very critical condition." Officials said that the gunman, Kyle Pierson, had targeted his debate teacher, Tracy Murphy.
Mark Pierson and his ex-wife, Barbara, released a statement regarding the shooting on Monday.
"We are shattered by the tragic events that took place on Friday at Arapahoe High School. Our thoughts and prayers are with Claire Davis and her family They, and she, have suffered unimaginably, and we pray for her full recovery," the Piersons said.
"We also pray for the entire Arapahoe High School community, as we know your lives are forever changed by this horrific event," the statement continued. "As parents, we loved our son Karl dearly and we are devastated by what happened Friday."
"We cannot begin to understand why Karl did what he did. We ask for privacy during this unthinkably difficult time and hope that you will respect our need for time to grieve," the Pierson's said.
Mark Pierson also contacted the Denver Post about his son, telling reporters that police needed to "answer questions" about Murphy's interactions with the gunman.
"I'm not the guy who is going to have the answers on this," he said. "Tracy Murphy is the key player."
[The Denver Channel, The Denver Post]