We'll probably never know for sure, but the sword used in this crime probably wasn't a "real" nihonto (Authentic Japanese blade, not a replica) and probably wasn't even sharp. But it'll cut you pretty good with a good swing anyway, though the injuries would not be very clean.
If it had been a "real" Japanese sword, the death toll would probably be four or five. They'll cut so efficiently that it takes little effort to cut someone badly enough that they can bleed to death in just a minute or two.
No doubt someone will push to get all martial arts supplies banned, including valuable heirloom and antique swords owned by collectors.
CJ