They were killed by Mexican gang members, many of whom come across the border illegally to sell drugs or purchase weapons.
But the PC side is more worried about alleged "racism" than the actual body count, and ease by which the gangsters sneak into the US
The pc world is more concerned about where their coke supply will come from, so they keep quiet about the wars in mexico, it's called conflict resources, the west ends up getting the cheapest prices so long as war prevails