Uhh, don't flip out? No one has died from weed, so don't ever EVER think that again for one second. And if you think "what if I'm the first one?!" then just stop it right there, millions upon millions of people have smoked, and I'm sure a few have felt like you have, and yet they didn't die. Just like you didn't die.

I don't know what panic attacks are like since I've never had one, but just convince yourself nothing is wrong. Thats all my advice, don't flip out, its just weed.