I don't get this. Did he kill them intentionally--was it his plan all along? (And if so, wouldn't he have just taken their money and shot them without driving all that way?) Would his sentence have been that harsh if he'd, say, raped and murdered someone intentionally? Not in today's court system.
This is bad and awful and serious-jail worthy, of course--but why is this more serious than Charles Manson's sentence?