Daniel Gerson, the co-screenwriter of Disney and Marvel’s Big Hero 6 and a contributor to several Pixar films, has died at age 49.

Gerson died of brain cancer in Los Angeles on Saturday, his family announced.

Gerson and his writing partner, Robet L. Baird, co-wrote Pixar’s Monsters Inc. and the 2013 prequel Monsters University. The writing duo is also credited for 2017’s Cars 3. Other credits include Chicken Little, Cars, Open Season, Meet the Robinsons, Up, and Inside Out. Baird also provided the voice of a few small roles in his own films, including janitors Needleman and Smitty in Monsters Inc. and the desk sergeant in Big Hero 6.