It appears the officer informed him it was store policy that unconcealed handguns were not allowed. Presuming that management had conveyed that information to the officer it suggests he might have been committing trespass. While signs may not carry legal weight actual notice appears to have been given.
If the guy did not have a CCDW then he should have informed the officer, who would then need to revise his instruction from "cover it up" to some other action.
Mommy and aunt did him no good by getting into their own argument with the LEO - and they need to go buy a lottery ticket because their luck seemed to be the only thing standing between them and being arrested for obstruction/interfering.
What I'm still trying to get an understanding of is why the ANG dood became involved in subduing our OC hero - if his assistance was not specifically ordered by the LEO then he at least technically committed assault & battery, kidnapping, probably impersonation of a police officer, and at least one federal count of deprivation of civil rights.
(Why do I bring this up. you ask? Because unless Ossifer Friendly specifically orders you to assist in an arrest he is attempting to effect you do not receive the protections that might be available under citizen's arrest laws. Ossifer Friendly could charge you with obstruction/interference - and most likely would if your unsolicited help resulted in either the BG getting away or Ossifer Friendly getting hurt. Restraining someone's freedom by force without authority of law is one of the elements of kidnapping. Being in the ANG, even if you are an ANG MP, does not give you any authority to act and if you were acting as a member of the ANG you were violating the Possee Commitatus Act.)
stay safe.