Investigators are reviewing 300 witness statements related to the deadly shooting at the Clackamas Town Center.
The Clackamas County Sheriff's Office said any release of information related to the investigation will not happen before early 2013.
Jacob Roberts, 22, opened fire in the mall Dec. 11. He shot and killed Steve Forsyth of West Linn and Cindy Yuille of Portland.
Kristina Shevcheno, 15, was also shot, and she survived the attack.
Deputies are sorting through a large number of reports, as well as forensic results.
Detectives said they are working on developing a timeline of events available for release, while also trying to determine possible motives in the case.
Roberts' roommate called a police tip line to report the man had been acting "weird," according to court documents. The roommate said Roberts had been selling his possessions on Craigslist.
Police believe Roberts stole the AR-15 semiautomatic rifle used in the shooting from a friend who lives a few blocks away. Sean Cates told police Roberts had said he "needed a gun and needed to get out of town," according to a search warrant.
Cates purchased the gun legally, according to police.
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