On 19 June 2016, the clear mountain air in the remote Mexican town of Nochixtlán was thick with the smell of burning tyres. Mounds of dirt and burnt-out cars formed an impenetrable barrier across a main highway in the southern state of Oaxaca.

‘Residents of the community, social organizations and teachers were carrying out a blockade,’ explains Harbert Jiménez Rodríguez. He is a rural teacher and press officer for Section 22, a radical branch of the dissident teachers’ union CNTE, which has fought for teachers’ rights for decades. The important road had been closed by teachers’ protests for several weeks when the state unexpectedly responded with a deadly attack.