The thing about this case is, the media has everyone right where they want them. Clicking on this story and sharing it. This is a media gold mine, and for the most part they have stayed far afield of reporting anything that may soften the hatred the public has for him. From what I've read in in-depth stories posted early on, Ethan has gone through a serious depression after the accident and became a recluse. The way one person ( a drugged out 16 year old) experiences remorse and regrets might be different from the way someone much more socially polished and mature expresses it, which might be through writing heartfelt letters to the families of the victims, or straightening their act out and vowing to have a positive impact on the world.
But that doesn't mean Ethan wasn't heartsick about what happened. But you'll never read that in major media stories now, because that might make the paying (clicking) audience sort of shuffle their feet and walk off in dismay at the sadness of the case.