The shooting took place at Canyon Springs High School in north Las Vegas, near Alexander Road and 5th Street.
The NLVPD reported that the shooting took place outside the school building, close to the baseball field.
Police responded to the shooting at around 2.40pm local time (10.40pm BST).
The victim, who is yet to be identified, was an 18-year-old man who was declared dead after being transported to a nearby hospital, according to the NLVPD.
It is currently unclear whether he was a student at the school.
In a statement, the police department said: “The NLVPD is investigating a shooting near Canyon Springs High School.
“Public stay away from the area.
“Media can stage on the east side of the school.”
It is currently unclear whether any other individuals were shot.
No information has currently been released regarding the suspect, and no individual is being held in custody.
Headteacher Greg Hunter released a statement to parents on behalf of the Clark County School District.
He said: “Canyon Springs High School is currently on lockdown as law enforcement respond to an incident near the vicinity of campus.
“It is an active investigation and police ask people to stay away.
“We will notify you once there is more information.”
More to follow…