The image led to the arrest of several people on charges of murder, robbery, illegal gun possession and drug offences.

Mr Ruiz’s shadow can be seen in the corner of the shot as a man identified by authorities only as “Pedro” points his handgun towards the mother of four and her son.

“Shoot!” Ms Ruiz is reported to have said in anger at the gunman.

San Cristóbal de las Casas has seen a wave of murders in recent months, including the slaying of a public prosecutor last summer.

Citizen groups are preparing protests against the rise in deadly crime in the city following the murder of Ms Ruiz.

“Her four children are mourning their loss and facing a future without the presence and protection of their mother,” a statement by 50+1 Chiapas, a state association that defends women’s rights.

Mexico recorded 34,515 murders in 2020, an average of 95 a day.