Zócalo, Mexico City, 13 August 1968. I'm in there somewhere with my wife-to-be (later, ex-wife) Judy, who was in Fayerweather but wasn't arrested. This was a gigantic student movement against the corrupt PRI government and university system, inspired to some extent — like the uprising in France — by the Columbia University uprising. We met some of the Mexican students at the Zócalo rally and agreed to meet them the next day for a big march that was planned. We waited for them at the appointed place and they never showed up so we did other things. That night we saw on TV that the march had been fired upon by government forces and something like 30 demonstrators were shot (memory vague, long time). This was seven weeks before La Noche de Tlatelolco[1,2], where hundreds were killed.

1. Elena Poniatowska, La noche de Tlatelolco: Testimonios de historia oral, Biblioteca Era, México D.F. (1971). Mentions the Zócalo rally but not the subsequent march or fatalities.
2. Tlatelolco massacre, Wikipedia, accessed 10 August 2019.
3. Mexican Movement of 1968, Wikipedia, accessed 10 August 2019.