A GUNMAN who shot and killed two people at a mall was a 19-year-old man who lived with his mother and arrived at the shopping centre in a taxi about an hour before opening fire, police said.

But police could provide no immediate insight into why Darion Marcus Aguilar, of College Park, killed a man and a woman on Saturday at the mall in Columbia, Maryland, about 20 miles west of Baltimore, before apparently killing himself. Police have yet to find any ties between Aguilar and the two people he killed.

Aguilar fired six to eight shots from a 12-gauge shotgun, killing Brianna Benlolo, 21, of College Park, and Tyler Johnson, 25, of Mount Airy, Maryland, police said.

Both were employees of Zumiez, the skate shop where the shooting took place. A third person suffered a gunshot wound to the foot, and four more were hurt in the ensuing chaos.

Aguilar had a backpack filled with crude explosives..

Officers searched Aguilar's home where they found more ammunition, and seized computers and documents. Police believe he legally bought the shotgun himself last month.