A high school sophomore shot and killed himself around noon Tuesday at Seven Lakes High School in the Houston suburb of Katy.

Steve Stanford, a spokesman for the Katy Independent School District, said the student, a 16-year-old boy, went to a secluded area adjacent to the school's cafeteria courtyard before shooting himself with a handgun. Stanford said the boy left a note.

Another student who witnessed the shooting ran to a school nurse for help, and the nurse and an assistant principal called 911. A Life Flight helicopter transported the boy to Memorial Hermann Hospital, where the boy later died.

No other students were harmed or threatened before the shooting, Stanford said, and Katy ISD police are investigating how the boy got the gun on campus. Katy schools are not equipped with metal detectors.

Seven Lakes, in the 9200 block of Fry Road, was placed on "lockdown" status immediately after the shooting, Stanford said, with all interior and exterior doors secured. Students remained on lockdown until 1:30 p.m., he said, and were released as usual at 2:30 p.m.