Cartel leadership have openly stated that any such thing would be the height of counterproductive stupidity on their part due to the overwhelming response that it would elicit.
The last confirmed incident was in the 90s. There was an incident in Texas a couple of days after Trump was inaugurated but this seems a little lacking in concrete details or threat: across the river, no video evidence, no injuries, no bullets recovered, no suspects, no identification, just a broad "description" of the shooters as "likely cartel members".
Because there's just not enough room in the budget for things like community engagement, rehabilitation programs, and similar things, so we have to spend millions on military surveillance gear to compensate for the absence of community engagement, rehabilitation programs, and similar things. Isn't it obvious?