Singer Christina Grimmie, a YouTube star who rose to fame on season 6 of The Voice, was shot and killed after an Orlando, FL, concert Friday night. Grimmie, who had opened for pop rock band Before You Exit at the Plaza Live concert venue, was signing autographs for fans when an unidentified gunman opened fire, fatally wounding The Voice alum before shooting and killing himself, reports CBS News Grimmie's brother, Mark, quickly tackled the gunman, who shot and killed himself during their fight. Orlando police credit his heroic reaction with preventing the gunman, whose identity and motives remain a mystery, from hurting others."We don't know if he was just a crazy fan that followed her on Twitter or on social media. We really don't know," Orlando police spokeswoman Wanda Miglio told CBS Orlando affiliate WKMG-TV . "This is a very tragic event. This should have been something that was fun and exciting, and for something like this to happen is just a tragedy."Grimmie's publicist, Heather Walsh, issued a statement concerning the tragic news via email early Saturday. "It is with a heavy heart that we can confirm that Christina has passed and went home to be with the Lord," Walsh wrote. "She was shot at her show in Orlando, and unfortunately didn't survive the gunshot wounds. We ask at this time that you respect the privacy of her family and friends in their time of mourning."Grimmie, 22, is best known for making the final three on season 6 of The Voice, where she competed on the team of Maroon 5 frontman Adam Levine. She first rose to prominence on YouTube. Her cover video of Miley Cyrus' "Party in the U.S.A.," uploaded in 2009, garnered the attention of her first management agency, reports People . The video has since amassed more than 12.2 million views.