Gun in stands

At halftime of the game, we were informed that someone in the stands had a gun on them and that they were arrested during the first half of the game.

My primary concern about this is that none of the officials on the field were informed of this while this was taking place and that the game was allowed to continue with a potential threat near or at the game site.

My question is: What can we do as officials if something like this is brought to our attention? Is there any procedure as to how something like this can be brought to our attention so we can act if needed?

This is a situation that needs to be handled by law enforcement personnel. If they deem the threat to be mitigated, they will let play continue (which is what happened here). They would have cleared the whole stadium if they thought there was a continuing threat.