CRITICAL: FROTHING MOUTH AND SEIZURE IN MY DOG

My dog quickly started going through a serious seizure. He's with saliva coming out of his mouth and can't move. I don't know what to do. Please help! Is this a sign of something really bad? I'm so scared, he's my best friend. My Canine Companion is Experiencing a Convulsions, Frothing at the Mouth It's incredibly frightening to witness your do