Nikolas Cruz has been formally charged with carrying out a massacre at Marjory Stoneman Douglas High School in Florida.
An indictment handed down by a Broward County grand jury charged Mr Cruz with 17 counts of premeditated murder and 17 counts of attempted murder. It means Mr Cruz may face the death penalty if he is convicted.
A former student who had been expelled from the Parkland high school, Mr Cruz is accused of killing 14 students and three school employees during a rampage last month.
Prosecutors have not yet announced whether they plan to seek the death penalty, but Mr Cruz’s public defender has said his client would be willing to plead guilty to avoid execution.
In a report, a deputy said Nikolas Cruz “appeared to be smiling and giggling” in jail.