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When three people happened upon 17-year-old Gabriella Arellano’s body in an East Side alley Sunday morning, the teen had been missing for more than a week.

Police found Arellano, 17, with a gunshot wound to the head between the 11000 blocks of Green Bay and Mackinaw Avenues around 10:15 a.m. Sunday, per a police report. She had been missing for more than a week.

Arellano’s mother had dropped her off near 106th Street and Avenue O in the East Side neighborhood the afternoon of Oct. 17th, according to a missing persons report.

Arellano had planned to return home that day, the report stated, but had stopped answering phone calls, using social media or showing up to her job at a nearby convenience store. It was not the first time she had been reported missing, per police documents.

Arellano’s mother filed the missing persons report Oct. 21st. Around 1:12 a.m. Sunday, a police report states that Arellano appears to have been walking southbound with two unknown people in hoodies in the alley where her body ultimately was found. All three appeared on private surveillance footage wearing face masks, according to the report.

Arellano appears to stop on the camera, then walk toward the two people she was on the west side of the alley. Moments later, surveillance footage captures the two other people running southbound through the alley, the report stated. A neighbor told Calumet area detectives that their home surveillance camera only captured the sound of one gunshot.

Three people found Arellano’s body the around 10 a.m. Sunday and called authorities, according to the report. An autopsy conducted Monday ruled her death a homicide due to multiple gunshot wounds.

Arellano’s family declined to comment when reached at home. No one is in custody, police said, and Calumet Area detectives were investigating.