No students were hurt. School principal Curtis Case and vice principal Vicki Kasper were rushed to the hospital. Kaspar was reported to have died shortly after 9 p.m. CST.
A witness said Case herded dozens of students into the school kitchen after gunfire broke out on campus.
Police said they found the shooter's body in a car where he killed himself about a mile away from the campus.
The shooter was identified as Robert Butler Jr., 17, the son of a police detective. Butler had transferred in November from a high school in Lincoln.
Students were released from the school lockdown about two hours later.
The Associated Press contributed to this report.