On 3 June 1991 at 4pm local time, Mount Unzen erupted, forming pyroclastic flows that rushed down its slopes, killing 43 people including the Kraffts, as well as their fellow volcanologist Harry Glicken, who had accompanied them to observe the eruption.
https://en.wikipedia.org/wiki/Katia_and_Maurice_Krafft
Well.
They have a cool documentary called ‘The fire within’