There are a lot of people in the world with mental health problems that surface when certain trigger situations arise. 

It is like someone being in jail for decades then suddenly finding themselves free. Depending on how they got into jail in the first place their first thoughts may be about revenge.

We probably do not need to know everything that motivated this man to draw conclusions about why he did what he did. Nor are there new lessons to learn from this incident.

The only questions is how many more mass shootings like this are needed before the US adopts stricter gun controls?