Based on everything I've read, it should have been covered by the local cops since it was outside of the protected zone. But also, whomever was in charge of the Secret Service there is still supposed to maintain control and give direction, even to the locals.
Sounds like the USSS called attention to that area, the locals were aware, the USSS didn't follow up to make sure the locals were actually on top of it, then the cop that supposedly confronted the assbag decided to save his own skin AND do nothing to draw attention to anyone else.
Whole lot of clusterfuckery occurred. Seriously, if the cop was going to pull a Uvalde and hide, couldn't he have blown up the radio for assistance or fired a random shot into the air or screamed like a banshee? Not saying that the last two are good options but they're obviously better than shitting your pants silently.