People die. It happens. Sadly tragedies and people responsible for them, are just as inevitable.
However, that said, we can only mourn and reflect.
Our best course of action is to give the dead proper burials, serve justice upon the perpetrator and take precautions to reduce the chances of this happening again, however slight a reduction it is.
Pointless debating gets us nowhere, guns or not, this happens, and we must deal with it.
I'm not a religious man, but I will give what support I can for the victims of this dreadful event.