How is this possible without explosives? Even with vehicle mounted machine guns it seems like a crazy high number. Did the protestors get boxed in somehow? And across so many locations, that seems to require a crazy amount of coordination to kill so many in so little time.

The coordination is the thing here, that's many units being instructed to carry through in the same manner.

As for the numbers:

  Interior Ministry reports say security forces confronted demonstrators in more than 400 cities and towns, with more than 4,000 clash locations reported nationwide

As to the how, the article suggests some deaths immediately occurred in crowds - firing, dispersing, funneling, crush injuries, etc. leading to many intakes to hospitals and treatment tents etc ... followed by execution of the injured.

It's grim stuff.

Some years past the waves of the Rwanda massacres saw almost a million people killed in bursts across 100 days, mostly with machetes and hand guns.

The numbers reported here are absolutely feasible, the reporting is certainly questionable; bad things happened, but was it at the claimed scale?

I don't think killing that many people requires much coordination when one side has guns (let alone machine guns) and a lot of soldiers

It's absolutely terrible but at the scale of a large country it's not logistically hard to get to that many deaths in a couple of days. Iran is a big country with population around 93 million.

The article says "36,500 killed in 400 cities". That's 91 people per city.

They executed every protestor that was arrested or in the hospital (estimated at ~28k.)

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