Same thing happened at my Mothers house at Christmas. My brother was cooking a roast, pulled it out to add the gravy same as you did, and it exploded. Luckily nobody was hurt. Luckily I arrived after the mess was cleaned up.
I had heard that Pyrex changed the glass formula a few years back and its these newer, cheaper ones that explode. The older ones are supposed to be safe. Not sure if that is true or not but I am sticking to metal. I have never had a metal lasagna pan blow up on me. Yet.
[SIZE=3][SIZE=2]Wood fired pizza oven,Copper Weber Gold, Green Weber Performer, Black Weber Silver, Green logo'd 18 inch Weber Gold, and a UDS of course.