I had been reading at the library at lunch, and was set to go back to work, heading for the down escalator, when I heard a woman yelling "Stop him. He stole my phone. Call security."
Sure enough, a young man comes barreling along and heads down the escalator. I headed down the escalator after him, taking multiple steps at a time, keeping up with him, but letting him stay ahead. I didn't personally want to catch him. I figured he could probably kick my butt, and I also figured the easiest way to stop him was to have the security guards do it. I knew that to leave the library he needed to go by the guard station - where you have to show the contents of your bag, if you have a bag, to prove you're not stealing any books.
I chased him from 7 down to 3, which is where the "main exit" guard station is. We encountered no one else on the escalators, fortunately. He slowed down, walking to the guard station, with me 25 feet behind him. I heard another man, a guard I think, shout "Stop him!" and I shouted "He stole a woman's phone!" and the guards stopped him. He complained to them, "What are you doing, man?"
The woman showed up, maybe a minute later, having taken the elevator down, complaining about the difficulty of moving quickly in heels.
So I left. I hope she got her phone back. I had my eyes on him all the way down the 4 flights, and I didn't see him toss anything.
Of course, I didn't see him steal the phone, either. Maybe he was innocent. But the flight made him look guilty.
Don't know the full outcome of the case,
but that was my lunchtime downhill race.