The shooting happened around 11 pm Friday near Merced Avenue and Shirley Street.
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Officers say a fight had broken out between at least two people at the party leading up to the shooting.
A 16-year-old and a 17-year-old boy, later identified as Renzo Arellano, were both hit by gunfire.
Investigators say Arellano died at the home from his injuries.
The 16-year-old is expected to survive.
Officers say social media played a role in the party, which had an estimated 100 guests.
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"It was evident that it was a large Halloween party with a bunch of juveniles, most of them were underage," said Merced Police Lt. Joey Perez.
"It's very important for parents to monitor social media because that's how these kids put out the information fast on where the party is at. That's what we believed happened in this case."
Police say after shots rang out, people took off running in all directions.
Detectives are looking for surveillance footage and any leads to help track down the shooter.
"In the end, a 17-year-old lost their life, didn't get to live their full life, over what? We don't know, but obviously, there was nothing that important that should have taken his life," said Perez.
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The Merced Union High School District confirmed Arellano did not currently attend any of their schools.
Action News has learned that Arellano had just turned 17 earlier this month.
Anyone with information about this shooting is asked to call the Merced Police Department.
A GoFundMe account has been set up for Arellano's family.
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