According to the backinfo I got, the armed gangsters who are seen in the video entering the establishment with the intent to stir shit were cops.
The incident happened in Pachuca, Hidalgo, Mexico. A young man appears to stand up to the gangster cops, and gets pistol whipped which sends him to the ground to die. The cop may have discharged his weapon while smacking the man with it, fatally wounding him.
The killer cop and his accomplices then flee the murder scene like the shits that they are. ACAB!
Props to Best Gore member @ramiroromo for the video: