If you're familiar with the case, you'd see that it would be difficult (albeit not impossible) to do it himself. But the ever skeptical Dr. "it's all swampgas" Hynek investigated it and was thoroughly impressed.
So, too the Air Force:
"There is no doubt that Lonnie Zamora saw an object which left quite an impression on him. There is also no question about Zamora"s reliability. He is a serious police officer, a pillar of his church, and a man well versed in recognizing airborne vehicles in his area. He is puzzled by what he saw, and frankly, so are we. This is the best-documented case on record, and still we have been unable, in spite of thorough investigation, to find the vehicle or other stimulus that scared Zamora to the point of panic." ~ Hector Quintanilla, Jr., Head of the Air Force's Project Bluebook.