Chances are, probably he got mental illness.
No sane person would such thing like that.
Edit: Just read article again, yup he has mental illness.
A law enforcement source with knowledge of the investigation told CNN on Saturday that the gunman had suffered from mental health issues. A few years ago, he was hospitalized for treatment after allegedly talking about harming someone, according to the official.
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It's not clear whether the state government or his family committed him for treatment or whether he committed himself. It's also unclear under what circumstances he was released.
Authorities have found no link to domestic or international terrorism, the official added.