A foul ball off the bat of Seattle's Brad Miller shattered the glass in a dining area located in the mezzanine section, somewhere between home plate and the visiting dugout. You can hear the reaction of the crowd, gasping in shock, and you can see the reaction of Brad Davis, wincing right after. Judging from the broadcast, it sounds like it also made a commotion of glass and dinnerware as people reacted to/tried to avoid the incoming ball.
This is the part where your old man talks about the carnivalization of sporting events and how back in the day there were no "dining areas" at baseball games. Your dining area was your seat. You dined on hot dogs. Back in Korea, we ate out of our helmets. None of this California-rolls-at-a-table nonsense. Someone probably woulda caught that, if they were payin' attention!
No one appears to have been hurt, which is good—though one lady in the back, in a red Angels shirt, appears to either be crying or wiping debris/drinks off her face—but I always thought those glass partitions were stronger than that. Apparently not, and they would later have to tape the glass up to prevent further damage.
I don't know what would be scarier: sitting in front of the glass and having that happen to you, or sitting somewhere close inside, but not paying attention and all of a sudden a baseball shatters the window.