Beyonce, Gwyneth Paltrow, Michelle Williams Join All-Star Effort to Combat Gun Violence (Video)

Conan O'Brien, Jennifer Aniston, Reese Witherspoon and Will Ferrell also appear in the video.

Hollywood actors and entertainers have joined forces for Demand a Plan, a grassroots effort to curb gun violence in the wake of the Sandy Hook Elementary School shootings.

The effort is spearheaded by the Mayors Against Illegal Guns campaign, launched in July after the Aurora, Colo., movie theater shooting. Since then, a petition demanding gun reforms has gathered more than 700,000 signatures.

Among the stars in the 90-second PSA: Beyonce, Jamie Foxx, Gwyneth Paltrow, Michelle Williams, Jon Hamm and Conan O'Brien.

"How many more?" they ask in the stark, black-and-white video. "How many more colleges? How many more classrooms? How many more movie theaters? How many more houses of faith?"

Jennifer Aniston, Reese Witherspoon, Paul RuddWill Ferrell, Sarah Silverman, Ellen DeGeneres, Julianne Moore and Chris Rock also are among the dozens of stars asking viewers to "demand a plan" for gun law reforms.

According to, the movement seeks to pass gun laws that require background checks for every gun sold in America, ban assault weapons and high-capacity magazines and make gun trafficking a federal crime.

The video is released on the same morning that NRA executive vp Wayne LaPierre blamed gun violence on Hollywood and recommended that armed guards be stationed in every school in the country.