It's put a spotlight on mental illness. In this country, 45 million adults are mentally ill. 11 million of those cases are considered serious.
CBS Evening News anchor Katie Couric reports on how those who need help most are falling through the cracks.
"Oftentimes, when we have tragedies like this people will say there were no warning signs," CBS News correspondent Ben Tracy said. "Well, in the case of Jared Lee Loughner there were plenty of warning signs."
"Loughner would laugh to himself at inappropriate times," Tracy said. "He would clench his fists and make faces just out of nowhere."
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It is still unclear how big a role mental illness played in Jared Loughner's shooting rampage.
"When you look back on it now, you say, oh, he was disturbed, he was unbalanced," Tracey said.
One of Loughner's former classmates said that he was nice to Loughner, in case he shot people.
Tracy added, "But there's big leap from a guy in your class who you find creepy to a guy who shows up and starts killing people indiscriminately."
"When he showed up on Saturday with a semi-automatic pistol and an extended clip, that was the first time the public knew anything about the threat and a that time, it was really too late," CBS News Justice and Homeland Security Correspondent Bob Orr said.
The Tucson shooting is the latest tragedy linked to a gunman believed to be mentally ill. In 1993, Colin Ferguson killed six commuters on a New York Train. In 1998, Russell Weston killed two at the U.S. Capitol. In 2007, Seung-Hui Cho murdered 32 people at Virginia Tech.
"The two cases are hauntingly parallel," Orr said. "Cho was a chilling character when you saw the pictures at Virginia Tech where he was posing with the guns. I had the same kind of flash back to that when I saw the mug shot of Jared lee Loughner. Their actions can't be defended in any way but, was enough done ahead of time to try and short circuit that danger and to help the individual? And in Loughner's case the answer seems to be no."
"In retrospect it's easy to connect the dots," Dr. E. Fuller Torrey, psychiatrist and founder of the Treatment Advocacy Center said. "If anyone could have put those all together it would have been pretty clear what should have happened."
Loughner slipped through the cracks in a society and health system that still fails to help people with serious mental illness. Nearly half of those who should be treated are not.
"We are doing a miserable job," Torrey said. "The public should be concerned about what a poor job we do in treating these people and what we are looking at in Arizona is only one of the consequences."
For every 100 American adults, 20 have some form of mental illness. Five have disorders classified as severe. They rarely pose a danger. But those odds increase without proper treatment.
"I am the mother of an adult who has been diagnosed with sychizoaffective disorder," Karen Gormandy said. "Because he was an adult, the only way he could have gotten treatment is if the police came and took him away in handcuffs. And that was it."
Privacy issues, access to treatment and the stigma of mental illness are major barriers for families and friends looking to intervene.
"They are afraid to report somebody because people are afraid they are going to ruin their lives," CBS News medical correspondent Dr. Jon LaPook said. "Also, there's some fear maybe the person will come back and do something to them."
25 states will not a person to be involuntarily committed unless he or she is in obvious danger, or they are not getting their basic needs met.
"The disease itself carries with it a lack of insight and denial," LaPook said. "So people say I'm perfectly fine I'm not going to get help. That's part of the disease. If you have high blood pressure and I say take this pill you're probably going got do it. But if you have schizophrenia you may say what you mean I am perfectly fine."
Privacy laws can also conceal patterns of alarming behavior.
"Personal rights are very important we protect people's civil liberties in this country," Torrey said. "But we protect them so well for many of these people who are severely mentally ill and don't know they're mentally ill - we're simply protecting their rights to be homeless, on the streets or in jail. We are protecting their right to be sick."
"Some states actually protect mental health records even more aggressively than records involving someone's physical health," CBS News chief legal correspondent Jan Crawford said. "We want to encourage people to seek treatment -- without being afraid that it's going to be used against them or disclosed to authorities at some point."
Mental health funding has been declining for decades. Since 2009, states have cut more than $2 billion for mental health from their budgets.
"Each, single part of the way where we fail somebody - we're all responsible," Karen Gormandy said. "I think we fail people with mental illnesses. we give up on them. Because it's just too hard."
"I've gone through Columbine. I went through Virginia Tech - I've gone through some horrible, horrible shootings. No I'm never shocked anymore," said Rep. Carolyn McCarthy.
Her husband was killed when he was shot on the Long Island Railroad by Colin Ferguson - who was paranoid and delusional.
"He just started shooting," McCarthy said. "And my husband was shot in the head. He died instantly."
Now another man, who appears to be mentally ill, has gunned down her colleague.
There is a growing movement to compel the mentally ill to get treatment. In New York, family members can petition the court to force a patient to take medication. But doctors and mental health advocates worry change won't come fast enough to prevent the next tragedy.
"Right now we need to have a much better system to sound the alarm," Dr. LaPook said.
"Until that happens we are going to keep seeing these and if anything they are going to increase in frequency," Dr. Torrey said.
Research show with proper treatment and medication, people with severe mental illness are no more likely to commit crimes than others.