Any museum/gallery with 'touchable' things needs a guard, right there, to prevent such happenings. The camera isn't enough. That fellow just looked to be curious, not unhinged.
May I humbly suggest: Rainbow Mars by Larry Niven. Contains as a central figure and menace the World Tree - responsible for destroying Mars and almost Earth. And also a good read.
Not to mention the massive dose of sodium hydroxide that pond is getting. Dead fish, anyone? How about dead water plants, and damaged trees all around? This is Pollution, people!
Now, in Canada, she'd be charged with 'excessive force', and he'd get free hospitalization and a free legal counsel to a)keep him out of jail, and b)sue her for her 'attack'. Oh, Canada!
There is something called 'the CSI Effect' that is altering the crime-versus-police world. The bad guys are learning to pick up their fired cases and wear plastic gloves to cut down fingerprint analysis. And on the other side, juries are expecting more and better evidence, looking for the special-effects miracles they've seen on TV.
Oh, Canada!