Note to the wise:... If an individual is parading crazily around with a weapon of any type, your decision to interfere, albeit potentially heroic is conducted at your behest alone. If that weapon happens to be a firearm, consider notifying local authorities. If you cannot physically overwhelm a lunatic with a weapon (by deviating their ability to agrees, you may be otherwise aggravating the situation more than helping. Cops are actually trained to deal with this crap.