John Lennon's widow Yoko Ono on Tuesday marked the 40th anniversary of the legendary musician's shock murder with a call for gun control. "The death of a loved one is a hollowing experience," tweeted the 87-year-old artist, who still lives in the Dakota building in Manhattan outside of which her husband was shot four decades ago. Ono, who witnessed her husband's murder at close range, also tweeted an image of the former Beatle's shattered and bloodied spectacles, which included the words: "Over 1,436,000 people have been killed by guns in the U.S.A. since John Lennon was shot and killed on December 8, 1980." In her tweet, Ono included a number of hashtags including #guncontrol now and #end gun violence.