IMO, any armed security should be contracted out to locally licensed professionals, either from a security company or (with OK of their employer) local LEOs.

This is not a DIY volunteer project. Way too many legal and liability problems.

Not quite the same situation, but our HOA had a security problem, and looked at various alternatives, and ended up hiring off duty local police to provide some additional security. Worked out well; they can use their police vehicle and are in radio contact with their dispatch. Plus, it helps our underpaid police.