I couldn't be friends with someone who tried even once. People willing to take risks like that in life, are time bombs looking for lives to destroy. Get the fuck out of their way, and keep them away. It isn't the drug, its the person, what they are capable of and what they will become capable of. They knew better, but still didn't give enough fucks about themselves or anyone around them.
Its been said, but seriously if you have to help, I'd get his ass arrested just to keep him clean. Keeps him at a distance, and protects you at the same time.