U.S. President Joe Biden on Tuesday called for a ban on assault weapons and tighter gun control measures as he stepped into the familiar role of grief counselor for a traumatized nation after a mass shooting left 10 people dead in Colorado. Biden spoke before leaving Washington for Columbus, Ohio, a visit where he will mark the 11th anniversary of the signing of the Affordable Care Act known as Obamacare. The mass shooting in Boulder followed a gunman's killing the previous week of eight people at spas in Atlanta, bringing new attention to U.S. gun violence. Flags at the White House were at half staff until sunset on Monday to commemorate the Atlanta shooting victims. They flew at full staff for a few hours on Tuesday morning before being lowered again to mark the Boulder killings. (c) 2021 Thomson Reuters, unless otherwise identified.