Transcript for Florida shooting is this year's 18th school-related shooting in the US
our thoughts and prayers are with the victims and their families in parkland, Florida, this morning. School shootings unfortunately are all too familiar as we've been talking about this morning. We remember, of course, the scene from columbine in 1999 and the one in parkland just yesterday. Our chief justice correspondent Pierre Thomas has a closer look at the disturbing statistics we're now seeing. Good morning, Pierre. Reporter: Robin, good morning. Those 18 school shootings this far shocking. Seven of those incidents classified as intentional attacks resulting in one or more deaths or injury. The other guns going off in schools and suicides or attempted suicides. They're becoming so common and in our quick search we found four thwarted attacks in the last year including one just yesterday where a grandmother in Washington state discovered her grandson was planning a deadly attack on his classmates with guns a guns and bombs. He was 18 years old and police say he had a journal where he talked about studying other mass shooters to increase his body count, robin. Oh, my goodness. With this shooter yesterday, Pierre, he seems to have been on the radar. He was expelled from school. There seemed to be so many warning signs and yet how do we still end up here? Reporter: That's the sobering question. Time and time again in these cases we find warning signs missed but these are not easy issues. Sometimes people say things and law enforcement follows up but sometimes there's not enough evidence to have them arrested. People will ask the question, how can someone with these anger issues and postings on social media not be flagged after having bought that assault rifle especially if those comments about wanting to harm someone turns out to be true if one of the many questions we have this morning. Thank you. Michael.
This transcript has been automatically generated and may not be 100% accurate.