he was already in jail on charges of doing a drive-bye 
A 15-year-old boy has been arrested in the killing of a Maricopa County detention officer who authorities say was targeted at random when he was shot in his own driveway.
Police Chief Daniel Garcia said Wednesday that the teenager will be charged as an adult with first-degree murder in the shooting of Jorge Vargas, 27. Investigators have worked hundreds of hours to try and bring closure for the victim's family, Garcia said.
"This arrest is the first step in that closure. We owe Jorge that," the police chief said at a news conference.
Garcia described the suspect as someone who wanted to be a gang member and had acquired a firearm. But police believe Vargas was a random victim and the teenager acted alone.
Vargas was attacked Aug. 8 at 4 a.m. while working on his car outside his home. He was wearing his uniform that identified him as a Maricopa County Sheriff's Office employee.
Investigators don't know what exactly happened in the driveway before Vargas was shot, Phoenix police Sgt. Trent Crump said.
The teenager had left a party around 3 a.m. while under the influence of alcohol and drugs, according to people who saw him there.
The suspect, whom The Associated Press is not naming because of his age, has been in a Maricopa County jail for the last few weeks facing an aggravated assault charge in an unrelated drive-by shooting, Maricopa County Sheriff Joe Arpaio said.
"I'm concerned whether the assailant knew our officer was an officer. It's tough to convince me he didn't know," Arpaio said. "Maybe one day, we'll get a motive from this suspect."
Crump said the teen's mother and a friend have also been arrested. Cathy Seymour was expected to be charged with hindering prosecution of her son. Ivan Montes, 20, was booked on charges of hindering prosecution and disorderly conduct, Crump said. They both are suspected of trying to get rid of evidence and helping the teen avoid detection from the police.
Another juvenile was arrested on suspicion of witness tampering but was released for a medical issue, police said.
Although investigators have not yet recovered the weapon used to shoot Vargas, Crump said they were able to use shell casings at the scene to tie the teen to the shooting. Investigators also served subpoenas for access to social media, but Crump would not elaborate on what relevance social media had in the case.
Vargas was an eight-year veteran who worked for the sheriff's Custody Support Bureau in a jail food factory, but he often came into contact with inmates.
Three members of Vargas' family attended the news conference but declined to speak with reporters.
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