Oh, and as for the invisible blood, my best solution would be to buy some dye or a UV or Black Light. The Black Light in particular can reveal blood stains even after they’re cleaned, and the fact that this next wave of invisible home invaders are spraying means they may be concerned that you’ll do something like that.

Does Raytheon do any kind of work with technology/chemistry? The kind which a lot of those acquaintances would say they aren’t allowed to go into details on? If so, the Invisible Man theory holds some water.

Oh, just realized I misread and hadn’t realized that you brought up the needle. Sorry, was on my phone when I typed that.

If it had been a beast of some kind, it sounds as if it was easy to overcome. Perhaps it was something that, as opposed to most forms of evolution where bigger and scarier was usually a more desirable trait…had evolved to remain hidden as a survival mechanism? Implying that they may be physically weak or at least fragile, explaining how you were able to send it running multiple times and kill it with ease despite the fact that it had the tactical advantage of being literally invisible.

You said that a piece of something fell off of your assailant that was visible in certain angles, right? Perhaps it isn’t a sit, but a formula of some kind that alters them inside and out?

My bet: Invisible Man scenario. Someone from a company that developed a full light spectrum camouflage suit was the stalker, either stole a prototype to regularly creep on you, or was being used as a deniable asset to test it by. And now that’s he’s dead the company has either just managed to catch up and is using their own stealth suited agents to clean up the mess….or they were always aware of him and are cleaning up the mess.

Either way: try laying out some powder or water or something else for them to step in/on. Make it so they can’t walk around your house with impunity.