How many people need to be involved and how large the area before geofencing is used as an investigation tool? I'd set the current bar lower than the capital ri

How many people need to be involved and how large the area before geofencing is used as an investigation tool? I'd set the current bar lower than the capital riots. Though how low is reasonable I don't know. I'm definitely opposed to finding a single individual, and an entire city. But I don't know how I'd feel about a single small building (say for a mass shooter event)