Authorities have confirmed that three people have been killed in a shooting at a mall in Columbia, Md. outside Washington, D.C. Both police and fire departments are on the scene. 
One of the dead, found near a gun and ammunition, is believed to be the shooter, police said.
Howard County General Hospital officials reported they are treating four people, including one who was shot in the foot. The other three individuals were not being treated for gunshot wounds, but for injuries related to panic at the scene.
Police confirmed that the shooting took place at Zumiez, a shoe store, and that the shooter had used a shotgun.
Shoppers were allowed to leave the Mall in Columbia after authorities determined there was no longer a threat, Howard County Police said on Twitter.
Police said a 911 call at about 11:15 a.m. EST reported that shots had been fired at the mall, a sprawling shopping center with about 200 stores about 30 miles north of Washington, D.C.
"We had officers quickly get into the area and we were able to identify three victims at an upper level store in the Columbia Mall, one of those victims appears to be the shooter," Howard County Police Chief Bill McMahon told reporters.
"We are very confident that it was a single shooter and there are no other shooters in the mall," he said.
McMahon said police did not immediately know the identities of the dead and did not know the motive of the shooter.
"So right now we still have many, many people still in the mall who have secured themselves inside stores," he said, adding that officers were helping people leave the building.
"I heard the shots and it was just a stampede...There were people running everywhere," said Antone Bishop, 19, who was shopping with his friend, Jared Malcolm at the Finish Line, a shoe store. "People were running out the of store...people didn't know what to do. People were crying. Everyone was just in a panic."
Bishop said he heard the shots and decided to go to the back of the store. He said about 20 people hid in a storage area for about 20 to 30 minutes until police came.
"At first I was in shock and then I was calm and level headed," said Malcom. I was not overreacting because I did not see it."
Nesreen El Sayad, a business woman who owns Sweet Treat, said she heard the shots and ran to a storage area to hide and wait for her husband to come get her. "I can't stay here. It is horrible. I just ran. I didn't see anything," said a visibly upset El Sayad.
Mohammed Zaidi, an 18-year-old employee of JC Penney, said customers ducked for cover after hearing gunshots. The store management then gathered people in the juniors department. "Some people were crying and really scared. I was really surprised, especially here. You don't really see that here."
The police department is advising people to avoid the area.
Customers inside the shopping center reported that the mall was in lockdown and some customers were directed toward the AMC Theater away from the scene of the shooting. Other customers reported hearing gunfire before fleeing the mall.
There is a heavy police presence at the mall with helicopters circling overhead and police officers searching car trunks in the parking lot.
Howard County Executive Ken Ulman said police would be holding a second news conference later this afternoon.