The Mexican troops likely were protecting smuggling cartels.
That was an act of aggression and needs to be dealt with accordingly.
It has happened before in other areas.
Exactly. Something should have happened with 30 minutes of the two groups parting. After wiping out the five, tell Mexico the very next time it happens, the entire unit to which the perps belong will be killed. We have Casper Milktoasts for military leaders.