URGENT: FROTHING MOUTH AND SEIZURE IN MY DOG

My dog quickly started going through a severe seizure. He's with saliva coming out of his mouth and can't stand up. I don't know what to do next. Please help! Is this a sign of something really bad? I'm so scared, he's my best friend. I Think My Pet is Having Seizures, Excessive Drool It's incredibly frightening to witness your dog/your pet/my