"high-capacity magazine" can refer to anything ranging from a fairly standard AR15 30-round stanag mag to a 200-round box magazine. Like, technically a high-capacity magazine is any magazine that holds more rounds than a standard magazine for a given firearm; but legally-speaking most states with laws regulating magazine capacity tend to define "high-capacity" as being more than 10~15 rounds for rifles.
So they could have had a normal Glock-19 magazine (illegal in some states as they hold 15 rounds, more than some states allow pistols to have) or a loose AR15 magazine in their glovebox from their last gunshoot, or they could have had a 100 round drum mag for their Glock.
Edit: California sounds like they have a universal 10-round magazine limit, which means a standard G19 magazine would be illegal.
Hold the fuck up. I'm almost certain I remember being told that military bases had no-flight zones over them that allowed them to shoot down anything that wasn't approved. Are you really telling me that I could fly a drone over Area 51 without being shot?