[Flag_This]

"officials explained that the man’s body had been “hurled back” by the force of the volcano’s pyroclastic flow"

Then I bet he was dead before the rock hit him.

"But during the surge "temperatures outdoors—and indoors—rose up to 300°C [570°F] and more, enough to kill hundreds of people in a fraction of a second," said Mastrolorenzo, who led the study, published in the June 2010 issue of the journal PLoS ONE." link

[ETL]

The pyroclastic flow may come afterwards.