A student in a Colorado high school opened fire at fellow students injuring at least one before killing himself, US authorities have said.
The shooter, identified by authorities as 18-year-old Karl Halverson Pierson, was carrying a shotgun and was looking to take revenge against a particular teacher.
The incident, which lasted for 14 minutes, took place in Arapahoe High School in Centennial, Colorado, at about 12:30 local time (19:33 GMT).
The latest attack has come on the eve of the first anniversary of the Sandy Hook Elementary school massacre, which killed 20 children, in Connecticut.
As soon as the authorities learnt about the firing, heavily armed personnel stormed the school ordering other students to evacuate the building with their hands over their heads.
A chilling sequence of events has unfolded over the latest attack.
"The student that was armed with a shotgun as he entered the west side of Arapahoe, immediately asked for the location of this specific teacher, and asked for that teacher by name. He made no effort to hide it or conceal it [the shotgun]," Arapahoe county sheriff Grayson Robinson told reporters outside the school.
"Word got around immediately that he was looking for the teacher."
"The teacher began to understand that he was being looked at and exited the school. One student confronted the armed student and was shot."
"The shooter is dead as a result of a self-inflicted gunshot wound, so there are no immediate threats at this time. Unfortunately we have one student who was injured."
A 15-year-old girl is in critical condition at hospital after gunshot wounds, said authorities. Officials earlier said two students were injured but brought down the count to one later.
Schools in the locality have been placed under lockdown following the gun attack. The Arapahoe High School is also near the Columbine High School, where 12 students and a teacher were shot dead by two gunmen in 1999.