My friend is suicidal. What should I do.?

So apparently this undisclosed person, let's call him/her (I don't even want to give away the gender) Sam, has been cutting him/her self, and has considered suicide. Sam's situation has been discovered by parents and 2 closest friends (me included). Sam is receiving treatment, but I don't know how I should respond/react to this situation, or how I should approach Sam.