what do I believe causes mass shooting? 1) Greatest cause is the heart of the person shooting. If the heart is corrupted with hate and confusion such acts are going to happen. Cane killed Abel with a rock or club. It was the heart. Second It is not so much mental illness as it is improper medication. Many are on SRSI inhibitors which mess with the mind. The mind is a complex thing. We do not have it right. Again it is not that they are mentally ill. But that they are taking either the wrong drug or the wrong dosage of the drug. But number one is the heart of the person. Thanks @krnel for the intriguing topic today.