A police officer and dog walk through a crime scene Tuesday in Las Vegas. Assailants shot six young people Tuesday who had stepped off a bus coming from a high school, wounding two seriously, in a midday attack just blocks from two elementary schools, authorities said.

Las Vegas ? Assailants shot six young people Tuesday at a school bus stop, wounding two critically, in a midday attack that followed a fight over a high school girl, authorities said.

School police arrested three teenagers in the fight hours before the shooting in a working-class neighborhood of northeast Las Vegas, Sheriff Doug Gillespie said. Investigators were still seeking two gunmen, who were believed to have fled on foot.

An 18-year-old man was in critical condition and a 17-year-old boy was upgraded to serious condition, both with gunshots to the torso, said Cheryl Persinger, a University Medical Center spokeswoman.

Four people, including at least two boys and a girl who are under 18, were treated for gunshot injuries to their arms and legs and released, she said. All four are students at Mojave High School, Gillespie said.

Authorities would not release any other information about the two victims who were still hospitalized late Tuesday.

Investigators initially looked into the possibility of gang involvement, but Gillespie said it appeared the shootings were the second stage of a confrontation over a girl.

Gillespie called the bus stop shooting “a carryover from what took place. This is not a random act.”

Those arrested after the school fight are about 16, Clark County School District police Lt. Ken Young said.

The shooting occurred just before 2 p.m., a couple of blocks from two elementary schools. Both were locked down temporarily but reopened in about an hour, district spokesman Michael Rodriguez said.

Mojave had some 2,300 students last year, about evenly divided among blacks, whites and Hispanics, according to district materials.

Archie Gorai, 22, who lives about a block from the site of the shooting, said he heard about eight gunshots while he was wrapping Christmas presents at his home.

“I told my wife it was gunshots. She thought it was firecrackers,” Gorai said.