No. Report promptly through the appropriate authorities; a poster is supplementary communication, not a prerequisite.
Verify the current authorized reporting contact through an official source before publishing it again.
No. Label them separately so readers can distinguish the event from the poster revision.
No guarantee is possible. Track distribution, issue replacements, and request removal of superseded versions where feasible.
Direct information to the verified reporting channel. Do not encourage public accusations, confrontation, or vigilante action.