More than three and a half years after the school massacre in Parkland, Florida, the shooter pleaded guilty to all charges.
The now 23-year-old Nikolas Cruz pleaded guilty in a court of 17 murders and 17 attempted murders on Wednesday.
With the confession of guilt, there will be no process to clarify the question of guilt.
The court will still have to decide on the punishment.
Cruz faces the death penalty, or at least life imprisonment with no prospect of early release from prison.
The then 19-year-old opened fire with a semi-automatic rifle on students and teachers at his former school, Marjory Stoneman Douglas High School, on Valentine's Day 2018.
He killed 17 people and injured 17 others.
The Parkland attack was one of the worst school massacres in US history.
Shortly after the bloodbath, survivors of the attack set in motion a nationwide student movement for stricter regulations on gun ownership.
Hundreds of thousands of people demonstrated in Washington a month after the massacre.
However, the gun law was largely not tightened.