First time poster thrown into deep waters (edited)

Hello, everyone! It's my first time posting and I appreciate you all taking the time to read this. My thoughts are so jumbled up right now, I'm not sure how to write this all down. It seems like the plot to a movie, but I assure you, this is very real and happening to someone I care about.

I'm going to attempt to give as much information as I can without revealing personal info.

I recently got back into contact with a close friend of mine. He and I had a falling out when we were younger, roughly 10 years ago, and haven't talked much since. He got back into contact with me out of the blue one day, then dropped off the face of the earth for a while, then got back into contact with me. After a few conversations, he let me in on his secret - he's being gang stalked.

I had no idea what gang stalking was at first, so I looked it up. Most of the information I found seemed to say that people who say they're being gang stalked are actually suffering from paranoia or schizophrenia.

I tried to be a sounding board for his ideas. I never dismissed them out of hand like the rest of his friends and family, I simply listened and tried to give him advice, basically "what would I do if this were happening to me?" It seemed to help. After the first few weeks of conversations, he seemed much calmer. He'd tell me how much the conversation was helping him, and how he can't believe he didn't think of this stuff himself. Things progressed from there. Every once in a while, he would let me know when someone would happen to trigger his paranoia, but other than that it was just a normal, awesome friendship. That is, until recently.

I had him and his girlfriend come stay with me for a few days, to reconnect in person and have a fun time. He woke me up in the middle of the night several different times because he was freaking out, saying "they were making his girlfriend twitch and laugh in her sleep right when he thought of something funny." Another time, he thought his girlfriend and I were sneaking into each other's rooms at night and having sex (this never happened - we never spent more than 10 seconds alone in the same room the entire time she was here). She also warned me before she came down here, on the phone, that he constantly gets paranoid and thinks his friends are having sex with his girlfriend. He assured me it wouldn't happen with me, but it did.

Things are much worse now. From time to time he seems normal, but the last two days have been bad. He suddenly thinks I'm "one of them". He'll randomly text me and ask me "how much are they paying you to do this?". He tells me about "street theater." How he'll be talking about something behind closed doors, then go into a public place and a group of people will bring up the very personal thing he just got done telling someone about at home. But it isn't just that - he's also picking apart what everyone says to him. The examples are so numerous it's hard to pick just one, but here's one that happened just today: we were on the phone, he was accusing me of being part of all this, and just before he did that I was telling him about a certain game I saw advertised online. He picked that apart and said it seemed like I was using the game as a metaphor, to basically tell him, "in code", "messing with you is a game to me and I'm going to laugh at you when you finally get locked up." he's done this to me multiple times, now. He said when he was staying at my home and his girl and him were doing laundry in my garage, he noticed a pair of her pants were slightly wet and asked her about it, she told him she didn't know how they got wet. Immediately after that I called him to the back corner of the garage to show him, inside my step-father's freezer, the 150lbs of fish he had recently caught on a trip to Alaska. He took that to mean "the pants were wet and I brought up fish because his girlfriend and I had just had "relations" behind his back." (completely untrue - it never happened) One minute he's telling me I'm helping him feel better, the next he's accusing me of being part of this, the next he's asking me to help him use logic to figure this stuff out.

He sees a psychiatrist, but not regularly. He's a regular marijuana smoker but hasn't had any lately. He takes anxiety medication.

Has anyone had experience with gang stalking? What do I do, here? I don't want to lose my friend again, and I definitely don't want to leave him all alone in all this. The rest of his family and friends are sick of hearing about it - his girlfriend threatens to leave him if he even brings it up to her again (because he's constantly asking her if she's cheating or "in on it").

And another part of me wonders if some or all of this isn't just in his head. How would I feel if this was happening to me and nobody believed me?

If you're going to ask me if he has any evidence, he actually has shown me two videos he's recorded, one of which seemed just like a guy was looking at him while he was smoking a cigarette, but another one actually disturbed me. A strange woman was walking down the street and suddenly just stops and stares at my friend, who pulls out his camera and records it. She stood there, blinking twice per second, for a good two minutes before she stopped staring at him.

EDIT: Had to change the post because of the sexual reference. I'm hoping I edited it to the point where it won't trigger anyone. I can edit further if necessary, but I completely removed the graphic description.