Popular Disney/Pixar screenwriter Daniel Gerson has passed away. Gerson died on Saturday following a battle with brain cancer, his family announced. He was 49 years old.

Gerson was responsible for writing popular films like Pixar's "Monsters, Inc.," which he co-wrote with Andrew Stanton. Gerson also was one of the three screenwriters who wrote the 2013 prequel, "Monsters University," according to Entertainment Weekly. One of his more recent projects was Disney's Oscar-winning film "Big Hero 6," which he co-wrote with Robert L. Baird, who was also one of the "Monsters University" writers.

Gerson and Baird worked together frequently, as they helped write films like "Chicken Little," "Cars," "Open Season, "Up," "Meet The Robinsons" and "Inside Out."

While Gerson is mainly known for writing the screenplays for these films, he did contribute voice acting for some minor characters as well, according to E! News. Gerson was even the one who came up with the beloved "Monsters, Inc." characters James P. Sullivan, Mike Waxowski, Boo and Baymax.

Gerson was born in New York and started as a staff writer for the NBC comedy "Something So Right," according to Variety. Eventually, he transitioned to animated films for Disney/Pixar, where his films alone grossed more than $2 billion worldwide.

Gerson is survived by his wife, his two children and his parents.