Anthony Pitts, 26, was arrested in Redlands without incident Thursday night, McMahon said. He is believed to be the one who pulled the trigger. His girlfriend, 29-year-old Danielle Cummings, and her friend, 28-year-old Reyna Mercado, were also arrested. All three suspects are Adelanto residents.
Makiya Walls, was shot and killed Wednesday night while sitting on a couch in her own home.
"Investigators determined there was an ongoing feud between the suspect and the victim's family, and the victim's residence was targeted by Pitts, Cummings and Mercado," McMahon said, adding that the young girl was not the intended target.
"Unfortunately in situations like this, emotions run high, and the mother of Makiya, obviously shaken by this event, but she was involved in some activity that amounted to credible terrorist threats against the suspect and the suspect's associates," McMahon said.
The victim's mother, 35-year-old Maesha McCullers, and her boyfriend, 34-year-old Christopher Hicks, were also arrested for making criminal threats against the suspects. Both are being held on $50,000 bail each.
Deputies responded to reports of the criminal threats between Wednesday night and early Thursday morning. Cummings identified the callers as McCullers and Hicks and she called 911 when Hicks arrived at her home, attempting to make contact, according to sheriff's officials.
Investigators determined the threats were credible and arrested the couple at a Victorville hotel at about 12:30 a.m. Friday.
Hundreds of people gathered to remember Walls, who was supposed to start seventh grade this week.
"You're not supposed to bury a 12-year-old. It's not supposed to be that way, and it is because my baby is gone, and I'm never going to get her back," the victim's mother said during the vigil.
Pitts allegedly used a shotgun to shoot blindly through the front window of the house in the 17000 block of Monaco Drive. There were several people inside, but the 12-year-old was the only one hit. She was rushed to a local hospital, where she later died.
Pitts, Cummings and Mercado were booked into the High Desert Detention Center for murder. Anyone with information about the ongoing investigation is urged to call (909) 387-3589 or sheriff's dispatch at (760) 956-5001. Callers wishing to remain anonymous can use the We-Tip Hotline at (800) 78-CRIME, or visit www.wetip.com.
All five people arrested are expected to be arraigned Tuesday -- McCullers and Hicks on felony criminal threats, and the other three are expected to be charged with murder, officials said.
A GoFundMe page has been set up for Makiya's family. To donate, visit https://www.gofundme.com/makiya-mela-walls.