Patrick Stewart, the acclaimed stage and screen actor known for his roles in “Star Trek: The Next Generation” and the “X-Men” films, has died at 86.

According to The Associated Press, Stewart died Wednesday in Los Angeles following what spokesperson Kelly Bush Novak described as a brief journey with Alzheimer’s disease and Lewy body dementia.

Stewart was widely known for playing Captain Jean-Luc Picard in “Star Trek: The Next Generation” and Professor Charles Xavier in the “X-Men” films. His career also included extensive stage work, including Shakespeare roles and performances on Broadway and in London’s West End.