My friends are all suddenly becoming ill and die?

About one year ago, on 12th of October, seven of my friends (four girls and three guys) and me had a sleepover at my place. My parents weren't home so they could not tell me not to do it. We did the usual things: we made pizza, we watched movies together while eating the pizza, played board-, card- and video games together (as far as possible), we played "spin the bottle" and "never have I ever" and I'm sure we did drink a lot; though way too much for my opinion (we're all over eighteen).
At 11.45 pm we decided to have a walk at night and to tell creepy stories, urban legends, and such things. And as we were passing through the forest which was nearest to my home, some of us even began to be slightly scared. I mean, we're all convinced that Slenderman and other creatures like that are not real but it was dark, silent like a graveyard, a little bit foggy, freezing cold and we were kinda drunk and soon came up with the "great" idea of secretly splitting up to scare the others to death. Also, there were rumors of a rapist that shall have roamed there. So basically we were doing the most stupid thing we could, challenging a bad fortune.
So the three of us (one girl and us dudes) were leaving the trail creeping between all those trees. Only one other friend knew of that so he would/should wait until we come and kind of act as if he didn't know what was happening.
I don't know when I first felt like being watched. I would spontaneously turn around from time to time to see if somebody was there but I never saw something other than trees. Sometimes I stumbled over branches and tree stumps. I would check myself for any serious harm and walk a bit faster as I told them to go on even without me. I'd catch up if necessary. Then I lost the others and I didn't know in what direction they went so I went by "try and error". It'd be good to even get out of the forest.
It slowly became windy and it started to rain but the worst was that the fog became denser and I couldn't see much. I had to take my glasses off to see anything. Any rustling would drive me to madness and paranoia and the feeling of being watched didn't go away. I don't know if I imagined things but at some point, I heard footsteps near me. I was so close to calling out to my friends but kept silent as I didn't know if it was them. When I couldn't bear it anymore I started to run as fast as I could and what or whoever it was, it would follow me. After some time I could barely breathe and had side stitches so I hid behind a tree and tried to calm my respiration. I heard the thing coming closer and closer and by the way, it moved, heavy and dragging, I knew that it could not be a friend. My heart stopped beating for a moment when it was that close I could hear it breathe. I even almost peed myself (should have gone earlier). When it seemed to be gone I still waited leaned against the tree fearing that it was lurking somewhere. If it was or not I can't tell. After what felt like hours I managed to find the trail and soon join the group of four again. The other did so too after a while.
They told me the following: The group of four would hear something running through the forest. As planned my friend would make unnecessary jokes, played the scared that tries to hide it and whatever. But the strange thing was that neither I nor the other two were there because the two were searching me after discovering that I was gone. I only told them that I lost the others.
You probably can imagine how the rest of the night was. None of us could fall asleep easily. None of us could sleep too far away from each other. Some tried to tell themselves that this wasn't real, some others checked the doors and windows multiple times.

But, as strange as this was, it is not the reason why I ask at this site.
After that night we all needed some space from each other. We did our school stuff and hanged around with the other friends we have. Life was going on and I was sure that I only imagined things. I really was confident that it all was not real and instead of a prank that went wrong.
On Wednesday at afternoon, I received a call from a friend, which I will call Alice from now on. Alice asked me if I was alright. She doubted that I've been telling the truth as I looked exhausted and pale. She offered to come over and talk and as I was feeling lonely since my parents still weren't home I appreciated the offer and agreed.
When she arrived I was making coffee and taking out some cookies. Then we would sit down in the kitchen and I'd narrate what happened on Friday night. I saw that it unsettled her. I can't blame her for that. She suggested, to be honest with my friends and if anything like that happened again I immediately should tell the police; indifferent that I am a guy in the twenties. There was only one strange sentence she said before she left. The last thing she said before saying goodbye. It was, that my smell reminded her of waxed wood and rusted iron. She said she remembered to have smelled the same scent while we were in the forest.

The next days I would ask my friends to come over and have a drink while I cleared the air. I've talked to two other about the thing in the forest, both of them are sick now and I can't reach Alice. Also their parents are behaving really strange lately. They normally greet me and tell me when Alice would have said something funny she experienced with me and how good friends we were, but now they are ignoring me. I would even go as far as to say that they look sad.

I mean, I know I don't need to ask but... is this normal?
Did someone of you experience such a situation?