Saturday morning on "Up with Chris Hayes," host Chris Hayes welcomed a panel including Amy Goodman of Democracy Now!; Howard Wolfson of the New York City mayor's office; Dave Cullen, author of Columbine and radio host Esther Armah. They discussed the role played by mental illness in attacks like the mass shooting Friday in Newtown, Connecticut and what society might endeavor to do differently to avoid these types of horrific attacks in the future.

Cullen said that most of these attacks are foiled in the planning stages, through what the FBI calls "leakage," i.e., when a plotter inadvertently exposes himself by telling another person about his plans. He said that in this way, the awareness created by Columbine tragedy has in some ways been helpful.

"But the other thing that we can do," he said, "is treating depression." The majority of these crimes are carried out by people Cullen calls "angry depressives," which is not like a regular person feeling sad and angry, but deep, clinical depression over a long period of time "and they get to a state of helplessness and hopelessness where they're distraught and they feel like they have no more options and so they're going to lash out in some, quote, 'crazy' way."

"After the Arizona shooting with Jared Loughner," said Goodman, "I interviewed the head of the National Alliance on Mental Illness in Arizona who said the massive cuts to care for the mentally ill in Arizona at that point were so drastic."

She went on to say, "But also, just to make this point, something like twelve hours before this massacre took place was a man in China who went into an elementary school. Maybe people saw it fleetingly on television, and he had a knife. He didn't have a gun. And he knifed 23 people, 22 of them children, at least at this point, at the time of broadcast, all survived. It was a knife, it wasn't a gun. Gun control is the answer right now."

Watch the video, embedded via MSNBC, below:

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