Tragic deaths in US cinema shooting provokes storm of mourning from stars

America's celebrities have joined actress Amy Schumer in mourning the tragic deaths of two women after a gunman opened fire in a Louisiana cinema.

John Houser, 58, opened fire during a screening of Schumer's film ‘Trainwreck’, killing cinemagoers Jillian Johnson and Mayci Breaux and wounding several others.

Schumer wrote of her horror online at the gunman's actions.

Director Judd Apatow also issued a statement saying the US needed to find a way to do "better".

"One of the reasons we make these movies is because the world can be so horrifying and we all need to laugh just to deal with it," he said.

"So to have this happen in a room where people were smiling and laughing devastates me."

Other high-profile celebrities posted about their sorrow on Twitter, including comedian Patton Oswalt, author John Green and singer Sam Smith.