In four decades of covering Asia as a journalist and writer, I had thought I'd seen pretty much every type of calamity that leads to mass deaths.

There was the week of communal violence targeting the Sikh community in November 1984, days after two of its members turned their guns on the person they were guarding - Prime Minister Indira Gandhi. Religious passions, a common human frailty, both instigated her assassination as well as the reaction that left thousands of Sikhs dead in the national capital New Delhi and some northern states.