Motive a mystery in Oregon mall shooting

NEW: Investigators recover a rifle and mask from the scene NEW: Victims' and shooter's identities to be released at 1 p.m. ET news conference The gunman was believed to be in his early 20s, a sheriff's official says A mall employee heard the suspect announce he was the gunman

Follow continuing local coverage on CNN affiliates KPTV, KATU, KGW and KOIN. See photos from the scene

(CNN) -- The masked gunman worked his way across the mall, terrifying holiday shoppers who had no clue where he'd fire next.

Entire swaths of Clackamas Town Center turned silent. The only sounds were the blasts from the man's rifle and the ensuing screams. Even the mall's Santa dropped to the ground.

"I thought I was going to die," mall employee David Moran said. "The gunshots were so loud, it was very scary. ... Kids were crying. Parents were crying, too."

Witnesses say at least 20 shots were fired Tuesday inside the mall, about 11 miles southeast of Portland, Oregon.

Kira Rowland was holding her 6-month-old baby in Macy's when the shots rang out.

.cnnArticleGalleryNav{border:1px solid #000;cursor:pointer;float:left;height:25px;text-align:center;width:25px} .cnnArticleGalleryNavOn{background-color:#C03;border:1px solid #000;float:left;height:25px;text-align:center;width:20px} .cnnArticleGalleryNavDisabled{background-color:#222;border:1px solid #000;color:#666;float:left;height:25px;text-align:center;width:25px} .cnnArticleExpandableTarget{background-color:#000;display:none;position:absolute} .cnnArticlePhotoContainer{height:122px;width:214px} .cnnArticleBoxImage{cursor:pointer;height:122px;padding-top:0;width:214px} .cnnArticleGalleryCaptionControl{background-color:#000;color:#FFF} .cnnArticleGalleryCaptionControlText{cursor:pointer;float:right;font-size:10px;padding:3px 10px 3px 3px} .cnnArticleGalleryPhotoContainer cite{background:none repeat scroll 0 0 #000;bottom:48px;color:#FFF;height:auto;left:420px;opacity:.7;position:absolute;width:200px;padding:10px} .cnnArticleGalleryClose{background-color:#fff;display:block;text-align:right} .cnnArticleGalleryCloseButton{cursor:pointer} .cnnArticleGalleryNavPrevNext span{background-color:#444;color:#CCC;cursor:pointer;float:left;height:23px;text-align:center;width:26px;padding:4px 0 0} .cnnArticleGalleryNavPrevNextDisabled span{background-color:#444;color:#666;float:left;height:23px;text-align:center;width:25px;padding:4px 0 0} .cnnVerticalGalleryPhoto{padding-right:68px;width:270px;margin:0 auto} .cnnGalleryContainer{float:left;clear:left;margin:0 0 20px;padding:0 0 0 10px} Emergency vehicles gather outside the Clackamas Town Center mall after a gunman opened fire, killing two people on Tuesday, December 11, in Clackamas, Oregon. The shooter died on the scene from a self-inflicted gunshot, said Lt. James Rhodes of the Clackamas County Sheriff's Office. The Clackamas Town Center mall is filled with emergency vehicles and law enforcement. Memebers of a SWAT team take position outside the mall. Lt. James Rhodes of the Clackamas County Sheriff's Office works with other responders in the parking lot of the mall. Panicked customers rushed to the exits when the gunman opened fire. Some people huddled behind store counters and hid behind racks of clothing. Authorities closed entrances and exits in the mall parking lot, said Lt. Gregg Hastings of the Oregon State Police. A law enforcement officer talks to people waiting outside the mall. Gunman opens fire in Oregon mall Gunman opens fire in Oregon mall Gunman opens fire in Oregon mall Gunman opens fire in Oregon mall Gunman opens fire in Oregon mall Gunman opens fire in Oregon mall Gunman opens fire in Oregon mall HIDE CAPTION << < 1 2 3 4 5 6 7 > >> Gunman opens fire in Oregon mall Two shot dead inside Oregon mall People leave Oregon mall with arms up Woman: Thought shooter was in flash mob

"I threw my baby into the stroller and just started running, because everybody was screaming and everybody just started to run," she said.

Inside Clackamas Town Center

By the end of the rampage, three people lay dead, including the gunman from a self-inflicted gunshot wound. One young woman remains hospitalized, Clackamas County Undersheriff Matt Ellington said Wednesday morning.

The motive remains unknown, but Ellington told CNN that the gunman had no connection with the victims.

The injured woman was identified as Kristina Shevchenko by officials at the Oregon Health and Science University Hospital. She remains in serious condition, the hospital said.

Authorities say they will identify the other victims at a press conference scheduled for 1 p.m. ET. Investigators have tentatively identified the shooter, believed to be in his early 20s, and will also identify him at the news conference.

The gunman wore a hockey mask and jogged through Macy's wielding a rifle, a woman told CNN affiliate KOIN.

As some panicked customers bolted for the exits, others ducked under store counters or hid behind racks of clothing.

The suspect announced aloud that "I am the shooter" as he ran through Macy's, said witness and store employee Austin Patty.

The shooter wore what looked like a hockey mask and a bulletproof vest, Patty said. He carried an assault rifle "like you would see in a video game."

As the shooting started, Patty ran out of the store, warning everyone in his path that there was a shooter on the loose and ordering them out of the store.

The sheriff's office confirmed that a rifle and a mask were recovered from the scene, Ellington said.

Investigators are reviewing surveillance footage to get a better picture of what happened, he said.

The Clackamas Town Center is located in Happy Valley, Oregon, a suburb of Portland.

Erin Quackenbush-Baker was in a vulnerable position -- in the middle of the mall at a kiosk with her grandmother and three young children.

Shooting inside Oregon shopping mall Shooting witness: People were screaming Witness: I saw woman on ground, shot

"My 5-year-old was covering her ears and crying. I was frantic to find a place to run, and I looked back (at) my son in my stroller and glass is falling over us," she said. "The shots were getting closer, and it sounded like he was getting closer."

"I felt like sitting ducks, where we were."

Timeline: Worst mass shootings in U.S.

During a brief halt in the gunfire, a man helped rush the family into a nearby Sephora store. That's where Quackenbush-Baker and her children hid for an hour, "waiting to see if we were going to be shot or not."

As word spread that the shooter was moving from store to store, customers at Sears burst into tears, Christina Fisher told KOIN.

"We were told to stand in a group by the top of the escalators and stay away from the windows out of the aisle. ... We stood there for probably a good 20 minutes," she said. "All of the sudden, somebody came through with a radio, yelling, 'Get down!' "

As the melee unfolded, some customers watched television news reports about the shooting from inside the Sears entertainment center, Tylor Pedersen told affiliate KGW.

Antonio Charro spotted a wounded woman near a cell phone store and tried to help, but to no avail.

"She had apparently been shot in the chest, and I couldn't get her turned over to help her," said Charro, who had been shopping at the mall with his daughters. "There was no one around. She wasn't breathing."

Clackamas County Sheriff Craig Roberts said about 10,000 people were in the mall at the time.

No law enforcement officers fired any shots when they arrived, sheriff's Sgt. Adam Phillips said.

The 1.4 million-square-foot mall will remain closed Wednesday as investigators look for clues about the attack.

Rowland said she's grateful she got distracted while shopping and didn't venture farther into the mall.

"I think if I hadn't stopped to smell that perfume, that maybe me and my baby wouldn't be here today."