well...
First, as far as I know there was only one side of protesters, they should have been very bright to to shoot themselves. There might have been shooters not belonging to the main police/army, groups but we have only one photo showing a shooter from a roof... of a police station.
Second. At first gov. said the gov. forces were carrying no weapons, then there started appearing photos proving the opposit, photos like this
https://d22r54gnmuhwmk.cloudfront.net/photos/8/yx/rm/WoYxrMsyGoAIVap-800x450-noPad.jpg?1466381698
Then gov. said those photos were 'false', taken from other places and other times. But around the above photos, we have further evidence: the claims of AP and this video
https://www.youtube.com/watch?v=XJMxOg8-D-g
We have also wits, and much more evidence, so
Third. Now the gov. has been forced to admit, first that gov. groups were carrying weapons, and now, we have an officer, Enrique Galindo, has on last hours of yesterday admitted that they have indeed shooted, arguing pathetic excuses.
Four, there are injured polices, yes, injured by ... stones. We shoud note, it's part of escalating gov. brutality against people supporting CNTE. And not the first time gov. shoots civilians, there was also the Ostula invasion past year.
But yep, the media will keep lying about this, adding to the many lies that have been said about the current conflict.