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When Coral Springs police officers arrived at Marjory Stoneman Douglas High School in Parkland, Florida, on February 14 in the midst of the school shooting crisis, many officers were surprised to find not only that Broward County Sheriff's Deputy Scot Peterson, the armed school resource officer, had not entered the building, but that three other Broward County Sheriff's deputies were also outside the school and had not entered, Coral Springs sources tell CNN. The deputies had their pistols drawn and were behind their vehicles, the sources said, and not one of them had gone into the school.

When a woman close to the Parkland, Florida, school shooter called an FBI tip line in early January, she described a young man with an arsenal of knives and guns who was "going to explode" and said she feared him "getting into a school and just shooting the place up."

My first day of teaching high school was September 11, 2001.

CNN's Gloria Borger profiles Special Counsel Robert Mueller, the man tasked with investigating Russian interference in the 2016 election.

Florida Gov. Rick Scott announced Friday a comprehensive plan to keep students safe, a week after a former student fatally shot 17 people at Marjory Stoneman Douglas High School in Parkland.