I doubt Jonah was watching the news reports at the hospital. I doubt he even knew her body was uncovered. I also doubt he contacted "legal advisors" immediately upon finding that Rebecca was dead. I think he was probably much too devastated to do anything except stay by Max's bedside.
I do agree with you on one point - Jonah didn't contact legal advisors upon finding out Rebecca was dead. He had likely done just after Max's accident.