My daughter had a similar experience as yours. She thought she was smoking the legal stuff you can buy in most head shops. She ended up pass out in a parking lot and her friends called 911. She was taken to the ER by ambulance and the doctor there said she had been poisoned by whatever it was she smoked. The next day, after she came home she told me what had happened and it was similar experience to yours. She was sure she had died, and from what the doctor told me she very nearly did. Her heart rate was dangerously high when she got to the ER. Turns out the guy that went to buy the shit bought some kind of powdered incense that cannot be smoked. He did not know what he was doing. You just never know what is in the shit you get on the street, be careful. It's much safer to grow your own.
Can't wait to grow some shrooms.