Bob Lazar talks about S4 and ET UFOs

Assuming Lazar is on the level, and some believe he isn't, there are other possibilities besides aliens from another world. The "others" might be more advanced humans who went underground, a past ancient civilization that isolated itself in some hidden place on the earth, a compartmentalized project (our own secret craft), some other species (reptilian?) that evolved intelligence and is hiding out using advanced stealth technology (bigfoot suits?), etc.