(CNN) -- Gunfire erupted in a Columbia, Maryland, shopping mall late Saturday morning, leaving three people dead and four injured, police said.
Howard County Police Chief Bill McMahon told reporters that the shooter apparently shot two people before shooting himself in a store on the second floor. The motive was unclear.
Police entered the mall and found three people dead, including one person who was found near a gun and ammunition. There was no indication of additional shots being fired. The scene was secure shortly before 1 p.m., police said.
"Think about this, on a Saturday afternoon at the mall, how many people may be in there," McMahon said at a press conference as mall customers and employees were still being evacuated. "Something like this happens and people run in many directions, and they also do what we train them to do -- to shelter in place."
A federal official briefed on the shooting told CNN preliminary information indicates the shooting may have been related to a domestic dispute.
Four people from the mall were transported to Howard County General Hospital, a hospital spokeswoman said in a statement. They were in good condition. One patient was a shooting victim, the others suffered injuries after the shooting. McMahon said one person had a seizure, another a sprained ankle.
Mall employees told CNN the gunfire erupted near a second-floor food court in the late morning, sending shoppers and workers running for cover.
"It's a mall shooting," one mall worker, identified only as K.T., told CNN. "No one knows what's going on. In today's world, you hear gunshots and you run."
The staccato of gunfire was followed by the cries and screams of children and adults running or ducking for cover, the employee said.
"A lot of kids were crying, and mothers were holding onto them," K.T. said. "I wasn't worried about me. I was just making sure everybody was OK."
Once the shooting stopped, SWAT team members moved from store to store.
"It was just crazy," said K.T., who snapped a picture of a bullet-riddled wall near the shooting scene. "It's one of those things you see on TV but never expect you'll go through."
Colin Reedy, another employee, said he heard a couple of booms and thought the sounds were from construction. Then, there were several more booms and people were screaming and scattering, he said.
The manager of the store where Reedy works closed the front gate, he said. When a police officer, not in uniform, came to the gate later to say the mall had been secured, Reedy said workers didn't believe he was a cop.
Laura McKindles, another mall worker, told CNN affiliate WJLA that she heard eight to10 gunshots.
"I have never experienced anything like this in my life," she said. "I was standing there talking to a customer and I started hearing all this banging coming from the food court... and people started running and they said somebody's down there and they got a gun."
Authorities initially reported that an active shooter was on the second floor of the mall in Howard County, according to CNN affiliate WBAL. Local scanner reports had authorities requesting multiple mass casualty units.
But one of the bodies believed to be the shooter was located near a gun and ammunition, police said. The identification of the person was unknown.
"We are very confident that it was a single shooter," McMahon said.
While McMahon spoke to reporters about two hours after the shooting, he said, SWAT teams and officers from various jurisdictions were still going store-to-store and evacuating people people who had taken shelter.
A 911 call about shots fired at the mall was made at 11:15 a.m., police said.
Images on Twitter reportedly from the scene showed mall employees and customers hiding in a stock room. The mall was on lockdown for some time.
The fire department, via Twitter, advised people to avoid the area.