Uh, no, you're wrong about him being a terrorist.
Let's go to the dictionary:
"ter·ror·ism
ˈterəˌrizəm/
noun
noun: terrorism
the unlawful use of violence and intimidation, especially against civilians, in the pursuit of political aims."
While you can be "terrorized" by a murder, the murderer need not be a terrorist.
The one thing that separates Paddock from your example of the 7-11 robber is the scope / magnitude of his slaughter.
Absent a political or ideological motive for the killings, the guy is a murderer, not a terrorist.