Yes, he was convicted of felony murder. The specific controversy was that he was sentenced to life imprisonment, despite being 16 at the time: http://rt.com/usa/aclu-pledges-help-without-parole-225.
Although, he was re-sentenced to a 30-60 year sentence with possibility of parole after a 2012 Supreme Court case: http://www.thealpenanews.com/page/content.detail/id/624360/N.... Big victory for criminal justice reformers. :-/
I don't actually like the you're-guilty-of-murder-if-your-cocriminal-kills-someone rule, but that seems like exactly the sort of case it's intended to work with.