Climbed out to 7,800' then made a sharp turn and dropped rapidly. My guess is they blew engine mounts on one side.
http://archive.is/LN1CM
http://archive.fo/LN1CM
https://web.archive.org/web/20190205140631/https://losangeles.cbslocal.com/video/4022587-pilot-killed-when-plane-nose-dived-into-yorba-linda-home-identified/