Broken window at Columbia Symphony concert

I forgot to mention (in my posting yesterday) that one of the window panes on the east side of the First United Methodist broke during the first movement of the Brahms 2nd Symphony at last night's Columbia Symphony concert. I talked to a fellow who was sweeping up the glass after the concert, and he said that he didn't find a rock anywhere. He guessed that the glass broke after someone (outside the building) put his/her elbow against the glass. I saw that @pdxclassical mentioned that glass incident.