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NEW: Deaths appear to be a murder-suicide, Glendale police say

"The school and neighborhood are safe," police say on Twitter

(CNN) —  

The deaths of two 15-year-old girls Friday on the campus of an Arizona high school are believed to be the result of a murder-suicide, police said.

The 10th graders at Independence High School in Glendale had single gunshot wounds and a weapon was found near their bodies, police said. A suicide note was located.

A shooting was reported just before 8 a.m., when the first classes were scheduled to start, said Officer Tracey Breeden. Officers found the girls under a covered patio.

“Although the investigation is not complete, investigators working the case say evidence found at the scene leads them to believe that one female took the life of the other female before taking her own life,” police said later Friday.

According to police, detectives learned the girls were close friends, and appeared to be in a relationship.

The Maricopa County Medical Examiner’s Office will make a final determination of the cause and manner of death. Police did not identify the girls, citing their juvenile status.

Authorities said it is believed no students witnessed the shooting. Police locked down the school for hours, with students waiting in classrooms with teachers.

Worried parents gather

Police asked students’ parents to gather at a nearby Walmart to await further information. Video from CNN affiliate KNXV-TV showed scores of people gathered in the store’s parking lot and more standing across the street. The school district said it would bus parents to the school, where they would reunite with their children.

“Our prayers are with the students, educators & families at Independence High School & all the first responders on the scene,” read a post on Arizona Gov. Doug Ducey’s Twitter account.

Independence High School opened in 1977 and is part of the Glendale Union High School District. More than 2,000 students are enrolled. Glendale is a city of about 230,000 just northwest of Phoenix.

CNN’s Michael Pearson and Azadeh Ansari contributed to this report.