A high school and an elementary school in the US city of Las Vegas have been locked down while police hunt for a teenager seen carrying a gun on campus.
According to local TV channel KTVN, the gunman entered the high school carrying a "long gun", possibly a rifle.
He is believed to have run away when confronted by campus police.
Swat teams have surrounded the schools. Dog units combing the area have reportedly found a weapon, but police fear the suspect may still be armed.
There are no reports of anyone being hurt at either Mojave High or Elizonda Elementary schools in North Las Vegas, Nevada.
There have been unconfirmed reports that the teenager could be a former pupil at the high school.
This is the third recent incident involving guns at a US school in the last week.
On Wednesday a 16-year-old girl died when an armed man took six students hostage at a Colorado high school.
Emily Keyes was shot when officers stormed the school in Bailey after more than three hours. The gunman also killed himself.
And on Friday, John Klang, the head teacher at a high school in Cazenovia, Wisconsin, was killed when he confronted an armed 15-year-old student as he entered the school.
The teenager, Eric Hainstock, was arrested and has been charged with murder.