CRITICAL: FROTHING MOUTH AND SEIZURE IN MY DOG

My dog quickly started having/experiencing a severe seizure. He's foaming at the mouth and can't stand up. I don't know what to do. Please help! Is this something I should call a vet about immediately? 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 witn