Hello, I'd just like to clear up this common misconception. Much like 18 USC § 331, which only targets the fraudulent defacement of coinage, criminal intent is also a requirement to be charged under the applicable criminal code for banknotes, 18 USC § 333. Pressing a penny at the zoo isn't illegal and neither is what the crazy person did to those banknotes. These codes are intended to prosecute attempts to change the face value of banknotes or remove metal from coinage to sell the scrap and pass off the coins as being their full value.

18 USC § 331:

Whoever fraudulently [emphasis added] alters, defaces, mutilates, impairs, diminishes, falsifies, scales, or lightens any of the coins coined at the mints of the United States, or any foreign coins which are by law made current or are in actual use or circulation as money within the United States; or

Whoever fraudulently possesses, passes, utters, publishes, or sells, or attempts to pass, utter, publish, or sell, or brings into the United States, any such coin, knowing the same to be altered, defaced, mutilated, impaired, diminished, falsified, scaled, or lightened—

Shall be fined under this title or imprisoned not more than five years, or both.

18 USC § 333:

Whoever mutilates, cuts, defaces, disfigures, or perforates, or unites or cements together, or does any other thing to any bank bill, draft, note, or other evidence of debt issued by any national banking association, or Federal Reserve bank, or the Federal Reserve System, with intent to render such bank bill, draft, note, or other evidence of debt unfit to be reissued, [emphasis added] shall be fined under this title or imprisoned not more than six months, or both.