Causes and conditions are combined, there are results.

Indiscriminate mass murder.
This is the result that the hunting ability was fully demonstrated.

Of course, in addition to that cause misunderstanding that distinguish between deer and human.
  Explosive attack appetite. He killed 60 people and killed himself as well.
His big fear. Extraordinarily big victim consciousness.
Thrill and suspense. Although the extent is unknown, the criminal seems to live in Las Vegas and it seems like gambling.
And misunderstood with his bloated ego. Intense impatience.
It is his thoughts, delusions, and the like that combine these to make it huge. This thinking, delusions will enlarge aggression and eventually will explode.