Two 15-year-old girls have been killed in an apparent murder-suicide at the Independence High School in Glendale, Arizona. Both were students at the school.

Glendale police found the two girls on a covered patio near the administration area, spokeswoman Tracey Breeden told reporters. Both were declared deceased at the scene. A single gunshot wound was found on each body, along with a gun nearby. The police declined to confirm if this may have been a murder-suicide, and said the investigation was still ongoing.

Police: it is unclear the relationship between the students. There were no other students around at the of the shooting. #abc15 — ABC15 Arizona (@abc15) February 12, 2016

The school was placed on lockdown, and students were ordered to stay in their classrooms. Local media reported the situation at the school was “relatively calm.”

Initial reports described the victims as “two teenagers,” but offered no details. One KNXV-TV source said that two female students may have got into an “altercation” at the cafeteria, which ended with gunshots. The police could not confirm if there was a relationship between the girls, however.

Parent telling us - 2 sophomore girls involved in double shooting. Sources say one died. School locked down. @abc15pic.twitter.com/9COnDjvLRs — Justin Pazera (@justinpazera) February 12, 2016

The school was placed on lockdown and students were not allowed to use their phones, one parent told KNXV.

Police were criticized for not getting the information out to the parents, and there were questions over the policy prohibiting calls or texting, keeping the families in the dark.

Scores of parents gathered at a Walmart near the school, designated by the police as a staging area, and expressing frustration that they have not been able to communicate with their children.

All the parents moving to the corner of Glendale and 75th Ave. they're all waiting for and update @abc15pic.twitter.com/Wv44XmTI7W — Nick Ciletti (@NickCiletti) February 12, 2016

#BREAKING: @GlendaleAZPD confirm they are working a double shooting at Independence High School @75th Ave/Glendale. pic.twitter.com/sIFJwiVQHa — CBS 5 News (@CBS5AZ) February 12, 2016

NOW: 75th Avenue CLOSED between Glendale Ave and Bethany Home Road. https://t.co/A8qr7ior61#abc15pic.twitter.com/yl76OXEnyS — ABC15 Arizona (@abc15) February 12, 2016

The shooting was reported just before 8 a.m. local time.

“This is an isolated incident,” Glendale police said in a statement, adding they were “not looking for a suspect.”

We are investigating a double shooting at Independance HS. The incident was isolated. The school and neighborhood are safe. — Glendale Police (@GlendaleAZPD) February 12, 2016

Glendale is a suburban city in Maricopa County, about nine miles northwest of downtown Phoenix. Independence High has approximately 2,000 students.