I concurgreat actor
obviously too soon to know, but I'd look at carbon monoxide poisoning first, given the scene and what has been reported
They also said that they had been dead for so long that if it was a CO issue the gas in the air could have dissipated before they were found.The article link said the authorities checked all the gas lines & found no issues.
Otherwise an open Rx pill bottle on a counter is suspicious.
Time will tell on what the authorities determines what happened beyond the obvious.