the Coke on Jay's shirt

How did the upper part of Jay's shirt get saturated with Coke?

You can see Professor Boaz inadvertently shaking up his Coke before he opens it; he is holding it in his hand while he gesticulates during his prolonged blather about the construction of Foucault Tower. He is *finally* starting to open his Coke, and we see a little fizzy Coke spurt out of the top of the bottle (around the cap), when we hear the first gunshot. But the radius of that Coke-spray is only about 8 or 10 inches, nowhere near powerful enough to drench Jay's chest.

You can't see what Jay is doing when we hear the first gunshot; he is almost entirely off-screen. But several seconds later we see that Jay has his Coke in his hand, held down by his waist, and it appears to be full. Eventually he drops it. Apparently he never got a chance to open it.