Being in the military does not make you more/less credible.
Being in intelligence services does not make you more/less credible.
The man could be a believer, like people who trust psychics, and genuinely think what he’s saying is true. He could be struggling with mental illness and believe himself. He could be a huckster trying to make money off UFO enthusiasts ( writing a book, giving paid lectures, interviews).
He hasn’t shown evidence. That’s a serious red flag. Perhaps that evidence comes tomorrow, but all previous claims like this just fade away without evidence being shown.