That could be a form of "cloaking" technology we do not understand. Tricking the human eye through manipulation of visible light is not outside the realm of current science. I'm pretty sure even the US military can do it.
Saying "I never saw one so they don't exist!" is pretty much the standard government/media line about anything unexplained...but it is a completely inadequate and unscientific answer.
Related and this stuff is happening more and more.
IMHO these are demonic hybrids showing up.
That a gubmit employee is reporting this speaks volumes!