Careful with that "knowledge of felony" stuff. This is the same line of reasoning that can lead to "no-knock" home invasions by the authorities (with uncertain and potentially lethal outcomes) and can cross the line for not allowing due process IMO. Actions have consequences, and in my totally inexpert opinion you are NOT expected to rise to the occasion to "validate" a potentially lethal weapon's status or the use(r) thereof--that is pure foolishness IMO. LE will probably treat a potential armed threat with a heightened sense towards potential escalation to lethal violence.
Arguably, that knowledge does not become "knowable" as potential evidence until you personally interact and gather information. Another reason why I would advise mind your own beeswax unless you are CERTAIN that a dangerous or criminal act is in progress.
Do what you like, I'm done with this thread.