When you say training I think Jamaat ul-Fuqra, the Pakistani non terror terror group with a number of camps in the US. There appears to be a camp in Oak Hill, CA, in the neighborhood.
Old thread Seeking Freepers for Jihadi Training Camp Observation and Information They'd have the sense to confine their firing to their land, and not likely at night
I remember that - thanks for posting link re: Jumaat al Fuqra.