4:14newsMay 21, 2018High school shooter studied mass shootings: Sources Dimitrios Pagourtzis, 17, who fatally shot 10 and injured 13 others at a Texas high school, researched tactics used by other mass shooters, sources told ABC News. Up Next in newsSuspected Texas shooter makes 1st court appearanceMay 18, 201810 victims dead in Texas school shooting, explosives found, officials sayMay 19, 2018Sandra Day O'Connor, 1st woman on Supreme Court, dies at 93December 1, 2023