The 22-year-old shooter who killed two people in an Oregon shopping mall Tuesday evening didn't know his victims, authorities announced Wednesday.

The Clackamas County Sheriff's Office identified the shooter as Jacob Tyler Roberts. Wearing a hockey mask and load-bearing vest, Roberts opened fire at 3:29 p.m. near the food court of the Clackamas Town Center. Using an AR rifle he stole from an acquaintance, Roberts killed Steven Forsyth, 45, and Cindy Yuille, 54, according to a sheriff's release.

Following 911 calls, deputies arrived at the scene at 3:30 p.m. and immediately began implementing an active-shooter protocol rather than waiting for SWAT officers. Deputies had completed active-shooter training at the Clackamas Town Center earlier in the year.

Prior to the attack, Roberts parked his 1996 Volkswagen Jetta in the mall's south lot near Macy's. He moved through Macy's toward the food court, where he fatally shot Forsyth and Yuille.

He then moved east past the Macy's Home store into a service stairwell that led to the lower floor of the mall. Roberts continued east toward JC Penny's where he was found dead 22 minutes after beginning the attack.

At some point, Robert shot Kristina Shevchenko, a 15-year-old who escaped outside near REI and was given medical aid by a deputy.

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