COLUMBIA, Md. >> A man carrying a shotgun opened fire at a busy shopping mall in suburban Baltimore on Saturday, killing two employees of a skate shop and then himself as panicked shoppers ran for cover, police said. Five others were injured.

Police were still trying to determine the identity and motive of the gunman who killed a man and a woman, both in their 20s, at a skate shop called Zumiez on the upper level of the Mall in Columbia, a suburb of both Baltimore and Washington.

Witnesses described hearing gunshots and screaming as panicked shoppers ducked into nearby stores and hid behind locked doors. Many found cover in stockrooms and barricaded themselves until the arrival of police, who searched store to store. By late afternoon, the mall had been cleared of shoppers and employees.

Howard County Police Chief William J. McMahon said at a news conference that authorities had difficulty identifying the gunman because of concerns he might be carrying explosives and were proceeding with an "abundance of caution."

"We do not know yet what caused the shooting incident," he said. "We do not have a motive."

Someone called 911 at around 11:15 a.m. to report a shooting at the mall. Police responded to the scene within 2 minutes and found three people dead — including the apparent gunman near a gun and ammunition — either inside or outside the shop, which sells skateboards, clothing and accessories. McMahon said police were confident there was a single gunman.

Police identified the victims as 21-year-old Brianna Benlolo of College Park, Md., and 25-year-old Tyler Johnson of Ellicott City, Md. Both worked at Zumiez.

Howard County General Hospital said it had treated and released five patients. One patient had a gunshot wound, while at least three other patients sustained other injuries.

The mall is at the center of the town and typically opens at 10 a.m. on Saturdays. It was busy with shoppers and employees when the shots rang out before noon.

Joan Harding of Elkridge, Md., was shopping with her husband, David, for a tiara for their granddaughter’s 18th birthday. She said she heard something heavy falling, followed by gunshots and people running.

"My husband said, ‘Get down!’ and the girl that worked in the store said, ‘Get in the back,’" Harding said. That is where they hid until police searched the mall and signaled it was safe to leave.

The mall was closed to the public as police looked in each store for people who might still be hiding, McMahon said. It will remain closed at least through the night.

McMahon said it wasn’t clear whether the gunman and victims knew each other. He said officers did not fire any shots when they arrived at the scene. Asked if the gunman shot himself, the chief answered: "That is certainly what it appears to be at this point."

Tonya Broughton of Silver Spring, Md., was with a friend getting facials for a "girls’ morning out," she said. "The only thing I heard was all the people running and screaming and saying ‘There’s a shooter! There’s a shooter!’" she said.

Wearing a gel face mask, she and her friend hid in a Victoria’s Secret store.

People were directed out of the mall and into a parking lot, where some boarded a bus and others walked toward their cars. Some people were seen crying. McMahon said detectives were interviewing witnesses as they emerged from the mall.

Laura McKindles of Columbia works at a kiosk in the mall. She said she heard between eight and 10 gunshots, followed by people running and screaming. She ran into the backroom of a perfume store and locked the door.

Allison Cohen, who works at the apparel store Lucky Brand Jeans, said she always felt safe at the mall.

"I truly never thought something like this would ever happen here," Cohen said. "It’s really, really shocking."

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Associated Press writers Jessica Gresko and Martin Di Caro in Washington contributed to this report.