There are a lot of skeptics, understandably. But if this message was removed from Russian media within two minutes of posting, I doubt it's Russian propaganda.

One commenter suggested it might be an FSB front, but what would they gain by doing this unless they are a rogue front of the FSB that believes what this message says, and the group is now fighting against Putin?

If that's the case, being part of the FSB would give them an advantage over any other group hoping to get close to Putin, eventually.

If their goals are as stated, Putin's death (or at least his removal from the Kremlin) would be on their to-do list.

I've wondered how long it would take for Russians to fight back against their repressive regime. Perhaps we now have the answer. Fingers crossed.