PORTLAND, Ore. (TheBlaze/AP) -- The gunman who killed two people and himself in a shooting rampage at an Oregon mall was 22 years old and used a stolen rifle from someone he knew, authorities said Wednesday. But in the days leading up to the attack, Roberts quit his job, sold his possessions and acted "numb," according those close to him.

Jacob Tyler Roberts had armed himself with an AR-15 semiautomatic rifle and had several fully loaded magazines when he arrived at a Portland mall on Tuesday, said Clackamas County Sheriff Craig Roberts.

The sheriff said the rifle jammed during the 22-year-old's attack, but he managed to get it working again. He later shot himself. Authorities don't yet have a motive but don't believe he was targeting specific people.

Two people - a 54-year-old woman and a 45-year-old man - were killed, and another, Kristina Shevchenko, 15, was wounded and in serious condition on Wednesday.

Roberts, wearing a hockey-style face mask, parked his 1996 green Volkswagen Jetta in front of the second-floor entrance to Macy's and walked briskly through the store, into the mall and began firing randomly, police said.

He fatally shot Steven Mathew Forsyth of West Linn and Cindy Ann Yuille of Portland, the sheriff said.

Roberts then fled along a mall corridor and into a back hallway, down stairs and into a corner where police found him dead from an apparent self-inflicted gunshot, authorities said.

New images from Roberts' Facebook page were also made public on Wednesday:

(Mediaite)

(Mediaite)

Roberts' ex-girlfriend, Hannah Patricia Sansburn, 20, told ABC News that she couldn't believe Roberts was actually the shooter.

"I don't understand," she said. "I was just with him. I just talked to him. I didn't believe it was him at all. Not one part of me believed it."

Sansburn said that Roberts recently quit his job at a gyro shop in downtown Portland and sold all of his stuff. He reportedly told her that he was moving to Hawaii. He had even purchased a ticket but it is unclear if he actually intended to move.