The gunman who shot and killed two people at a Maryland mall was a 19-year-old man who lived with his mother in the city of College Park and arrived at the shopping center in a taxi about an hour before opening fire, police said on Sunday.
But a day after Saturday's shootings, police could provide no immediate insight into why Darion Marcus Aguilar killed a young man and a young woman at the mall in Columbia, Maryland, about 20 miles (32 km) west of Baltimore, before apparently killing himself.
Police have yet to find any ties between Aguilar and the two people he killed, employees at a skate shop at the mall, Howard County Police Chief Bill McMahon told a Sunday morning news conference.
"We do know that one of our victims also lived in College Park," McMahon said. "We don't know if there's any connection there or whether that's merely coincidental."
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 on a lower floor of the mall suffered a gunshot wound to the foot, and four more people were hurt in the ensuing chaos.
The shooting happened around 11:15 a.m. EST (1615 GMT) on the mall's upper level just above the food court. The mall, which has more than 200 stores, was crowded with weekend shoppers; many took shelter after hearing the shots or seeing people fleeing.
Police, who were in the area on another case, responded to the emergency calls within two minutes and found all three bodies either in the store or just outside it.
Aguilar had a backpack filled with crude explosives, and authorities were initially concerned he had booby-trapped himself, McMahon said.
"These were homemade devices consisting of flash powder and household items, so they're not very sophisticated," McMahon said.
Overnight, police searched Aguilar's home where they found more ammunition, and seized computers and documents. Police believe that Aguilar legally bought the shotgun himself last month in nearby Montgomery County.
McMahon said he could not yet give further information about Aguilar, including whether he worked or was a student.
College Park is home to the University of Maryland's flagship campus.
The attack in Columbia followed a shooting at a New Jersey mall in November in which a gunman fired at least six shots without hitting anyone, sparking a mass evacuation of the complex, then killed himself.
There has been a spate of shootings in recent days at U.S. schools and universities. A student was shot dead on Friday at South Carolina State University in Orangeburg, and on Tuesday a teacher's assistant was shot and killed at Purdue University in Indiana. Suspects have been charged with crimes in both cases.