Zemeckis
Among the most destructive of the astra was the “brahmastra,” created by the god Brahma, a “single projectile charged with all the power in the universe. It was an unknown weapon, an iron thunderbolt, a gigantic messenger of death which reduced to ashes an entire race. There was neither a counter attack nor a defense that could stop it.”
The weapon produced “an incandescent column of smoke and flame as bright as 10,000 suns that rose in all its splendor. After, corpses were so burned as to be unrecognizable. Their hair and nails fell out; pottery broke without any apparent cause, and the birds turned white… After a few hours, all foodstuffs were infected.
“Any target hit by the brahmastra would be utterly destroyed; land would become barren and lifeless, rainfall would cease, and infertility in humans and animals would follow for aeons of time.”
The brahmastra was detonated at the end of the final 18-day battle of Kurukshetra. The Pandavas vanquished their enemy, the Kauravas, with the devastating weapon, but the few surviving Pandavas discovered that there was nothing left to occupy, and no one left to rule. The brahmastra had destroyed the entire Kauravas society, and turned the region (present day Rajasthan) to desert. The war also marked, in the Vedic system, the beginning of the current “Kaliyuga” age.
https://www.gaia.com/lp/content/evidence-nuclear-war-ancient-times/
Here is another good theory on the origins of tektites.