Darion Marcus Aguilar was familiar with The Mall in Columbia. He hung around outside, smoking with small groups, police said.
The revelation Tuesday provided the first solid link between Aguilar and the shopping center at the core of this Howard County community, though police say they still don't know what motivated him to kill skate shop employees Brianna Benlolo, 21, and Tyler Johnson, 25, before turning a shotgun on himself.
Howard County police said they have reviewed Aguilar's journal and are examining his cellphone and a home computer, but have found nothing that connects him with the victims. Of the journal, authorities said only that Aguilar "knew he was having mental health issues."
The new information emerged as customers returned to the mall a day after a somber reopening that honored the shooting victims and drew public officials from around the region. The mall had been closed for most of Saturday and all of Sunday amid a police investigation.
The Zumiez store where the shootings occurred remains closed.
Preliminary details released Tuesday by the state medical examiner offered a clearer picture of how the attack played out — leaving three young people dead as mall patrons huddled in fear.
Benlolo died from shotgun wounds to her neck and chest, said Bruce Goldfarb, a spokesman with the medical examiner's office. Johnson's death was caused by "multiple shotgun wounds," he said.
Aguilar wounded another mall patron in the foot. That person's identity has not been released.
Aguilar, 19, then put the approximately 3-foot-long shotgun to his mouth and killed himself.
"Cause of death was intra-oral shotgun wound; manner is suicide," Goldfarb said.
Full autopsy reports for Aguilar — including toxicology results — as well as on the two victims could take 60 to 90 days, Goldfarb said.
Howard County police have mostly communicated with the public through social media and have largely declined to elaborate on the brief dispatches issued on Facebook and Twitter.
The agency said it was keeping details about Aguilar's journal secret because they do not want news reports to muddle the memories of potential witnesses who could shed light on the attack.
Police said Aguilar arrived at the mall in a cab about 10:15 a.m. Saturday. Police said he carried a backpack that held a Mossberg 500 series pump-action shotgun.
He used an upper-level entrance near the mall's carousel and walked downstairs to the food court. According to police, he went back upstairs about an hour later and fired six to eight shots.
Police said they want to learn more about Aguilar's activities at the mall in the days and weeks before the shooting. They said they are working to determine whether he had ever been to Zumiez, though other news organizations have interviewed an employee who said he saw Aguilar around the store.
For more than a year, Aguilar had lived with his mother in the 4700 block of Hollywood Road in College Park — about a half-hour drive from the mall. Before that, Aguilar and his family lived in Silver Spring, about 20 minutes from the mall.
Aguilar did not have a driver's license, according to a Rockville gun shop owner who sold him the shotgun used in the attack. Aguilar used a state learner's permit for identification when he bought the gun Dec. 10.
Police did not say how often they believe he visited the mall. They emailed a flier with a picture of Aguilar to mall management, which distributed it to retailers, who asked employees whether they had ever seen the teen.
Detectives are also looking into Aguilar's financial records to trace his activities, police said, adding that they had determined that he was not shown in a widely circulated picture from Benlolo's Facebook page.
Amid the questions, the Columbia community is trying to regain a degree of normality. Some people who go to the mall regularly said Tuesday that they felt that resuming their routine was the best way to go.
A half-hour before the gate to the Panera Bread was raised Tuesday, Carol Jones and Sue Warren were there, catching up and waiting to get their morning coffee.
While some shoppers have expressed reservations about returning to the mall, the two Columbia residents said they didn't hesitate.
"Early in the morning, the mall is so peaceful and quiet," Warren said.
Baltimore Sun Media Group reporter Amanda Yeager contributed to this article.