The shooting at a Florida high school was the 18th of its kind this year in the United States.
At least 17 people were killed and another 14 injured when a gunman opened fire at Marjory Stoneman Douglas High School in Parkland.
Nikolas Cruz, a 19-year-old former student who was expelled, has been arrested in connection with the shooting.
It is not an isolated incident and takes the total to 18 shootings at schools in the 44 days of 2018.
Texas has already seen three separate shootings take place in its schools since the turn of the year, while California and Michigan have both had two incidents.