Colorado Gov. John Hickenlooper said the school shooting Friday in a suburb outside of Denver is particularly troubling because the state had spent millions over the last year in educating people to identify mental health issues that could lead to these mass shootings but the teenage gunman didn't exhibit signs of mental illness.

Karl Pierson, the suspected gunman, badly wounded a fellow student then shot himself to death at Arapahoe High School in suburban Denver Friday. Police say he may have been retaliating for bullying and for being kicked off the debate team months ago.

But Hickenlooper told CBS' "Face the Nation" on Sunday that Pierson didn't exhibit recognizable signs of mental illness.

“We haven't found – we're unaware of any connection that would suggest previous behavior or indicating something like this would happen,” he said. “He didn't seem to have a mental illness. He had a lot of friends, he was outspoken.”

“There are a couple of stories that he was bullied – that's a recurring theme we see sometimes with these shootings,” the governor continued. “But again there's no rhyme nor reason ... there's nothing that says, 'Ah, now I understand.' ”

Hickenlooper said the state had pent $20 million last year on mental health initiatives – on programs like 24-hour hotlines and drop-in and mobile crisis centers.

“We're really trying to intercept people with mental illness before they can cause damage to themselves or to others, and yet somehow this kid didn't exhibit any of those symptoms,” he said.

Colorado authorities are still searching for a motivation shooting at Arapahoe High School that left one student, Claire Davids, in a coma and in critical condition after being shot from close range in the face.

“We are looking for any connection,” Hickenlooper said. “Some people have suggested there is a copy-cat element to this. I don't see it ... it defies rational thought.”

Hickenlooper praised law enforcement officials' handling of the shooting, saying Sheriff Grayson Robinson and his entire team were trained and knew exactly what to do to limit casualties. One deputy sheriff posted at the school, he said, immediately ran toward the shootings and was there within a minute of the first shot.

“I mean, that's a remarkable response, and I think everybody from the sheriff out there, Grayson Robinson, his entire team, they deserve a lot of credit for what could have been much, much worse,” he said.

The shooting outside of Denver came one day before the one-year anniversary of the Newtown, Conn. tragedy, and the Sunday political shows featured dueling contentions about what should be done to reduce gun violence.

"There isn't one reason why we have such a horrendous rate of death from gun violence," said Mark Kelly, the husband of former Rep. Gabrielle Giffords, D-Ariz. "But I still strongly believe that the first thing we should do is require a background check before somebody can buy a gun, to prevent people who are dangerously mentally ill or criminals [from purchasing them]."

But gun rights advocates argued that a background check would not be effective, and that the country should instead loosen gun laws in order to allow more people to purchase them.

"We have to be able to protect ourselves, not rely on something like a background check," said Larry Pratt, executive director of Gun Owners of America. "If we're really serious about people who have some kind of problem, mental or criminal, they ought to be in jail."