Classical music question

At the end of Casino, where Robert Deniro is describing what happened to Vegas after the mob got squooshed and the place became an adult Disneyland, financed by junk bonds, there is a classical piece in the soundtrack, and I think it is a Mozart mass. Am I right, and if so, can anyone tell me what it is?

I heard it this evening on KUSC during their pledge drive but Jim Svedja did not back-announce it

It’s a part of the St. Matthews Passion, by JS Bach.