Jacob Tyler Roberts carried a Stag Arms AR-15 semiautomatic rifle and 145 rounds of ammunition when he entered the Clackamas Town Center and began firing indiscriminately, according to a massive report on the Dec. 11 rampage released Wednesday. He wore earplugs and gloves and carried no identification.

He fired a total of 17 shots, including a suicidal bullet to his head. A toxicology report found marijuana and a low level of cocaine, indicating use 36 to 48 hours before the shootings.

The 926-page document provides new details of how the terror unfolded inside the mall, how law enforcement coordinated their response to contain the shooter and how emergency medical workers quickly assembled to treat victims. But there is no answer to the essential question: Why did this happen?

Roberts had no history of violence or mental illness, no criminal history, no relationship to any of the victims and no known ties to the mall.

On Dec. 1, Roberts and his girlfriend broke up, and on Dec. 5 Roberts told his boss he was quitting and moving to Hawaii. On Dec. 8, he bought two 30-round magazines from a local gun shop, then two 20-count boxes of .223-caliber ammunition, ear plugs and paper targets at a big box retailer.

Police Reports - Clackamas Town Center Shooting

Below is the 926-page police report released by the Clackamas County Sherrif's office.

On Dec. 9, he bought two 30-round AR-15 magazines, four 20-count boxes of .223-caliber ammunition and more targets at a sporting goods store. He also listed his car for sale on Craigslist.

On Dec. 11, the day of the shooting, Roberts met a friend, Sean Cates, at a bar. At 1:30 a.m. Roberts and Cates bought beer at a 7-Eleven and returned to Cates' home to drink. Cates showed Roberts his AR-15, and Roberts later stole the rifle.

At 3 p.m., Roberts visted a friend, Tyler Eheler, who lives two miles from the mall. They talk about Roberts moving to Hawaii and smoke a small amount of marijuana. Roberts left Eheler's place about 3:15 p.m. and entered the mall at 3:28 p.m.

After crossing through Macy's department store, Roberts arrived at the food court an opened fire. The first 9-1-1 calls came in at 3:29 p.m.

Thirteen of the rounds he fired did not hit anyone, instead smashing store windows, facades and a glass-enclosed elevator. Bullet fragments were found in Taco Time and Tully's coffee shop. A Mini Cooper banner hanging in the mall was found riddled with bullet holes.

The entire mall erupted in panic, shoppers flooding out of the doors. So many people called 9-1-1, that the emergency system overloaded, sending Clackamas County calls to dispatchers in Lake Oswego and Multnomah County.

Clackamas Town Center shooting

The Clackamas County Sheriff's office provided this

.

Continuing coverage of the Dec. 11, 2012

One minutes and 12 seconds after the first 9-1-1 call, Clackamas County sheriff's deputies descended on the Town Center, leading a surge of police, firefighters and emergency medical responders.

As police began to draw tight their net, Roberts ran from the food court, which was littered with empty .223-caliber shell casings, broken glass and items abandoned by fleeing shoppers. He then moved down a corridor and into a service stairwell, where he killed himself, firing his 17th and final shot.

Just 22 minutes after rifle shots abruptly crushed the mall's holiday mood, police found Roberts' body near J.C. Penney.

The sheriff's office has spent nearly five months assembling and reviewing 281 police reports written by 114 officers from 15 agencies. Officers took 227 statements by witnesses and looked into 311 tips as the investigation unfolded.

The report contains chilling details of Roberts rampage.

One witness describes Roberts' demeanor and angry and violent, another reports seeing people getting bloodied as they tried to save Yuille's life.

As shoppers fled and took refuge inside stores, the huge mall fell silent. As officers entered under orders to "hunt and kill" the shooter, they reported the only sound was Christmas music. Also released were photos taken inside the mall and a timeline of the shooting.

"But what we don't have is his motive," said Lt. James Rhodes, Clackamas County Sheriff's Office spokesman. "He didn't leave a note and he didn't tell anyone about his plans."

Before Roberts died, he killed Steven Matthew Forsyth, 45, of West Linn, a marketing executive and youth sports coach; and Cindy Ann Yuille, 54, of Northeast Portland, a Kaiser Permanente hospice nurse.

He also wounded Kristina Shevchenko, 15, of Southeast Portland, who underwent surgery to remove bullet fragments from her liver and lung and was released from the hospital to recover at home.

In addition, Vanessa Ogden, 29, who managed the Justice store and kept panicked shoppers safe, endured such severe stress during the incident that she subsequently suffered as many as 70 small strokes and died Feb. 15. Physicians said the shootings triggered a kind of post-traumatic stress disorder.

Clackamas County Sheriff Craig Roberts expressed condolences for the victims.

"We felt it was incumbent upon us to take a look again at what happened at the Town Center," Roberts said. "We lost two wonderful people that day and we felt we owed it to their families."

Reporters Michael Bamesberger and Heather Steeves of The Oregonian contributed.