What qualifies as a "mass shooting"?

[gorobei]

http://www.fbi.gov/stats-services/publications/serial-murder/serial-murder-1#two

Basically, more than 4 people, with no significant intervening period between deaths, and with all the deaths in the same place.

the car used in the ucsb incident kinda spread the place of the deaths over a path of a mile or so.