How Did this Not Crack..???

I was checkin out OutkastChicken's 89 T Bird, I was wonderin how in the hell he shortened his front window. In the pic it looks like he is usin a angle grinder, how did it not crack. And if this does work, what type of blade do you use for the grinder?? Anyone now, I'm thinkin I'm gonna do it, if I can find out how he did. I've Emailed & IM'd him, I haven't waited long for a response, but I'm impatiant, and ready to start cuttin. Can anyone help me out.

Here's a couple Pics in his Profile, Kinda showin what he did..