Wow that is really creepy. Just your story made the hair on my arms stand on end. I have never had that happen to me personally but have friends who have had experiences with demons and ghosts and all sorts of evil creatures. Clearly he was letting you know they were aware of you and showing their power.
During a recent workshop I attended (I am a very new Empath but have been having paranormal experiences my whole life) someone gave me a book called, "The Unquiet Dead", a true book about a psychologist's experiences with patients possessed by disembodied spirits. She told me she knew what I was going through, with all of my angst, etc...Then, the next time the workshop met, she smiled at me from across the room and I saw a very brief glow in her eyes like what you are describing!!!!
I found it very interesting that she gave me this book without me having told her that I had been terrorized by a demon in my late teens/early twenties!
I agree with what BriarRose said about this being a demonic or evil presence letting you know they are aware of you and showing their power. Go with what your gut your tells you!
Sounds like a walk-in and they were testing you to see if you noticed. Good you ignored it. Now, I wonder why you? There are all matter of 4D critters that would use a meat suit to operate in 3D environments. Demons? Nahhh, what are them if not just something that is negatively charged. I've come across a clone being used as a 3D meat suit by "pumpking heads". That ended in them hightailing it out of here while being pursuited by the good guys.Not all "people" you see and meet are actually people. Now you know.
In the future you can call on Archangel Michael to surround you with White Light. This will put the demon on the run asap. We shine very brightly from the spirit perspective. As this is the time of the Awakening you will hear about this more often. It is always best to surround your home and person with white Light on a daily basis in the AM before starting your day and PM before going to sleep. This is a time of drawing the line between those of the Light and those of the Shadow realm. It is a good thing that you "found" us.
Throw some love into the wind.
Soldier of white light, its interesting some of the responses. Unfortunately we live in a world where white and dark meet. Now you know that all you meet out there are not human even though they look like human. That one is hard for some to fathom. I've made it a study to look and tell. Its also interesting how you know how to deal with that sort of thing. Its easy to tell and deal with them, the hard part is figuring out why this one and not that one. Take the following words to heart: TO KNOW, TO DARE, TO DO AND TO BE SILENT. That White Fire and the other instruments are very powerful. Some people you'll meet may ask and some demand you tell them. I just ask my higher self and deal accordingly.
You must know that the person may not have been aware this was going on. The way these critters operate is they stand behind the person and place all their attention on them while they make them do things. When they come across my field of view, I am the last thing they ever sense... pow! white powder.