Two students were critically injured and four others hurt when they came under fire as they left a school bus in Las Vegas, US police say.
Police are investigating if a school fight was linked to the attack
The six were all either middle or high school students and were shot just before 1400 local time (2200 GMT), the Associated Press news agency reports.
At least two people are believed to have taken part in the shootings.
Police are giving few details other than saying they are investigating a theory the shooting was gang-related.
It was not clear if the suspects had been on foot or in a vehicle.
Police said they were investigating if a school fight involving three male students earlier in the day, which resulted in three arrests, was linked to the shooting.
Clark County School District police lieutenant Ken Young told AP television news: "We are investigating the origin of the initial fight, and seeing if there was any tie to this incident this evening."
According to local newspaper Las Vegas Review Journal, the six students were shot near a bus stop on "Alexander Road at Walnut Road".
Two are believed to be in their late teens and the others are believed to be juveniles, it said, adding that one of those hurt is a girl.
Two male casualties were reportedly shot in the torso and the others apparently suffered less serious wounds, the newspaper added.
The Las Vegas incident follows a series of gun attacks in other US cities in the past week, the BBC's Peter Bowes reports.
A 19-year-old man killed eight people and himself at a shopping centre in Nebraska, and a further five people died at a church and a faith-based training centre in Colorado.