School Safety

Frank DeAngelis, center, who was principal at Columbine High School during the massacre almost 20 years earlier, fights back tears during a faith-based memorial service for the victims at a community church, Thursday, April 18, 2019, in Littleton, Colo. (Rick Wilking/Pool Photo via AP)

This combination of undated photos released by the Jefferson County, Colo., Sheriff's Office on Tuesday, April 16, 2019 shows Sol Pais. On Tuesday authorities said they are looking pais, suspected of making threats on Columbine High School, just days before the 20th anniversary of a mass shooting that killed 13 people. (Jefferson County Sheriff's Office via AP)

FILE - In this May 1, 1999, file photo, demonstrators gather on the Colorado State Capitol grounds in Denver, Colo., to protest against the National Rifle Association's annual meeting, which is being held in the city. Data shows that such shootings are less frequent and with fewer killed than in the years that preceded Columbine. Still, Americans worry about how safe schools are. (AP Photo/Eric Gay, File)

FILE - In this Dec. 14, 2012, aerial file photo, officials stand outside of Sandy Hook Elementary School in Newtown, Conn., where gunman Adam Lanza opened fire inside school killing 20 first-graders and six educators at the school. A Connecticut appeals court is scheduled to hear arguments on Wednesday, April 17, 2019, on whether parents of some of the shooting victims can sue the town for school officials' alleged failure to follow security protocols once the shooting began. (AP Photo/Julio Cortez, File)

In this April 9, 2019, photo, Grant Whitus poses for a portrait at his home in Lake Havasu City, Ariz. Whitus' marriage fell apart a year after he led his SWAT team into Columbine High School's library, where he was the first to find the dead children's bodies. (AP Photo/John Locher)

This combination of undated photos released by the Jefferson County, Colo., Sheriff's Office on Tuesday, April 16, 2019 shows Sol Pais. On Tuesday authorities said they are looking pais, suspected of making threats on Columbine High School, just days before the 20th anniversary of a mass shooting that killed 13 people. (Jefferson County Sheriff's Office via AP)

This combination of undated photos released by the Jefferson County, Colo., Sheriff's Office on Tuesday, April 16, 2019 shows Sol Pais. On Tuesday authorities said they are looking pais, suspected of making threats on Columbine High School, just days before the 20th anniversary of a mass shooting that killed 13 people. (Jefferson County Sheriff's Office via AP)

A student leaves Columbine High School late Tuesday, April 16, 2019, in Littleton, Colo. Following a lockdown at Columbine High School and other Denver area schools, authorities say they are looking for a woman suspected of making threats. (AP Photo/David Zalubowski)

Democratic presidential hopeful John Hickenlooper, right, hugs Michael Davis during a meeting with survivors of victims of mass shootings in Colorado Tuesday, April 16, 2019, in Denver. Michael Davis lost his daughter, Claire, in December 2013 during a shooting at Arapahoe High School in Littleton, Colo. (AP Photo/David Zalubowski)