Nearly 200 artists and music industry executives have added their signatures to a letter to Congress pleading to "Stop Gun Violence Now" in America. The letter was organized by Billboard for its latest cover story. The magazine's staff reached out to the artists and executives it covers to tell the U.S. government "to close the deadly loopholes that put the lives of so many music fans, and all of us, at risk." The letter arrives the day after House Democrats staged a sit-in in opposition to the GOP's refusal to vote on gun control. Read the rest of Billboard's open letter here.