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.
Mr Cruz confessed to carrying out the shooting when he was apprehended shortly afterward, according to an arrest affidavit.
The suspected shooter’s lawyers have described him as a troubled and “broken” young man and have argued the system failed him, noting that his behaviour repeatedly drew the attention of authorities.
Jail records released by the Broward County Sheriff’s Office describe Mr Cruz, segregated from other inmates, as at times appearing “logical and coherent” and in other instances exhibiting a “blank stare”. He has shown signs of restlessness and been heard laughing, the records say.
On the same day the grand jury handed down its indictment, Secretary of Education Betsy DeVos visited Marjory Stoneman Douglas High School. Her appearance frustrated some students who said said they were not able to air their concerns.
Survivors of the shooting have been the public faces of a renewed push for tougher gun laws in the shooting’s aftermath. Florida legislators have pursued measures that include raising the gun-buying age to 21, empowering courts to bar troubled people from owning firearms and arming some teachers.