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John-Michael Keyes started the 'I Love U Guys' Foundation following the death of his daughter, Emily, in a shooting at Platte Canyon High School in 2006. It aims to provide schools and law enforcement agencies with guidelines for a plan to respond in case of a crisis, like a shooting.

"I love u guys" was the last text message Emily sent.

Keyes says districts across the country need to reevaluate the measures they take following every school shooting. One thing he says may change following the incident at Sandy Hook is how the public is able to access their local school.

"That openness is part of the magic of a school," Keyes said. "But I firmly believe the controlled-access point is going to become a national conversation. Districts and communities are going to need to look at it. We live in different times."

School districts across Colorado have implemented some of Keyes' strategies, including using common terminology like "lockdown" and "lockout."