Students from the Santa Monica area participate in a walkout demonstration as part of the National School Walkout for Gun Violence Prevention campaign in Santa Monica, California on April 20, 2018. - Students across the US were urged to walk out of classes to mark the 19th anniversary of the 1999 school shooting at Columbine High School in Colorado which left 13 people dead. The walkout has been organized by students at Marjory Stoneman Douglas High School in Parkland, Florida, where 14 students and three adult staff members were killed by a troubled former classmate on February 14, 2018. (Photo by Mark RALSTON / AFP) (Photo credit should read MARK RALSTON/AFP/Getty Images)
