A man carrying a shotgun opened fire at a busy shopping mall in Columbia 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 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.

Witnesses described hearing gunshots and screams as 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.

A news release on Saturday night said that police found and disabled “two crude devices that appeared to be an attempt at making explosives using fireworks.” Police were searching the mall with dogs overnight, which is standard procedure, and the mall was to remain closed on Sunday.

Someone called the police emergency dispatcher at around 11.15 am (local time) 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 skate shop. Howard County police chief Bill McMahon said police were confident there was a single gunman.

Police identified the victims as 21-year-old Brianna Benlolo and 25-year-old Tyler Johnson. Both worked at Zumiez.

“She was all excited because she was the manager there,” John Feins, Benlolo’s grandfather said in a telephone interview from Florida.

“It’s senseless. It’s totally, totally senseless,” he said.

“I mean what can you say? You go to work and make a dollar and you got some idiot coming in and blowing people away,” he said.

Mr. 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. The police news release said it appears the gunman died from a self-inflicted gunshot wound.

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