Honestly, I'd start off with an email if possible. Just express your condolences and let the person know that you're there if you need them, you're there. If they need you they'll reach out. My dad died a couple of years back, and the last thing I would have wanted was people calling me offering their condolences. The way I looked at it, it was already on my mind on a constant basis, I didn't need every person I knew reminding me of it.
That was my first thought, but since I don't have his email and I don't use myspace to message him there, I thought maybe a text would suffice with a simple "You know I'm here if you need me, I'll drop whatever I'm doing to help" but I feel that might be rude.
As for the backstory, its nothing crazy there. The friend (Carlos) that told my girlfriend to tell me what happened is a bit of a selfish prick that everyone in our group of friends was sick of. He told us all he "needed a break" so he could figure himself out, which normally I'd be cool with if it was anyone else, but I knew he was doing this because the attention wasn't all on him anymore and he hates that. He'd done this pretty often too, just vanish until people would myspace message/email/call/text him asking where he's been and why he hasn't hung out, then get a big group together so everyone can say how much they missed him. Total attention whore.
Anyway he did this again for like the 3rd time in a year, and I expressed how sick of it I was to my girlfriend and other good friend and they were on my side. We weren't gonna cave in and feed his ego anymore. Hell I even made a bet that he'd come back to his myspace page at the very least a week before his birthday just so he could get all his lil 14 year old myspace girl friends to flood his inbox.. and i was almost right, he came back into the spot light 2 weeks before his birthday.. We didn't call him or anything like we said we wouldn't (no one did except this one girl thats on his nuts) so his birthday goes by and even though he text my girlfriend or messages her on myspace, my friend Jay and I never heard from him again. That is until word got back to us that he thinks we're pricks for not wishing him a happy birthday or anything. Flash forward to now and I still haven't talked to the guy. You might think its stubborn of me but in all honesty I was sick of the guy. He's my age (22) and acts like he's 16 with no plans on growing up, and I was sick of letting him hold me back, but thats a story for a different day.
The only person that stayed in touch with him at the time was a mutual friend of ours, Jeremy, who we'd both known since 2nd or 3rd grade and its his brother that was killed. I never planned on not talking to HIM for such a long time, but it just happened that way becuase the other guy (Carlos) is the type to make people choose sides. Neither him or I had seen Jeremy since high school and one day he walks into the job I had at the time, I got his number and told him to hang out with me and Carlos for old times sake. He did and Carlos "claimed" him, saying things like "oh guess who i found on myspace!" meanwhile I was the one who gave Jeremy his email just so he could surprise him with a message... I'm digressing.
To cut to the chase: When Carlos showed me how self centered he really is, Jeremy was kinda stuck in the middle and was convinced to take sides. I've tried to get him to hang out plenty of times back then, but when he said he'd come out he'd flake, so it wasn't very long before I just didn't bother, I'm too old to deal with teeny-highschool drama like that anymore.
I wouldn't be opposed to taking him out somewhere to take his mind off things, since I never had a problem with him, I just know it'll be a little awkward because of the way things went down over a year ago.