COLUMBIA, Md. — Authorities on Sunday identified the gunman who shot and killed two people at a Maryland mall as a 19-year-old man who lived with his mother in suburban Washington.

Darion Marcus Aguilar of College Park, Md., carried out Saturday's attack with a 12-gauge shotgun at a skateboard shop at the Mall of Columbia before killing himself, police said.

Howard County Police Chief William McMahon said investigators are trying to determine whether Aguilar knew either of the victims, who were both shop employees, and whether he had a criminal record. They offered no motive for the shooting.

"There are a lot of unanswered questions," McMahon said at a news conference.

It took hours to identify the gunman since he was carrying ammunition and a backpack containing homemade explosives, McMahon said.

Officers searched Aguilar's home Saturday night, recovering more ammunition and other evidence, police said.

The home is a two-story wood-frame house in a middle-income neighborhood called Hollywood, just off U.S. Route 1 and near the Capital Beltway. No one answered the door Sunday morning at the house, which had a Christmas wreath on the front door and signs that read "Beware of Dog" and advertising an alarm system.

Residents described the neighborhood as a mix of owners and renters, including some University of Maryland students. McMahon did not know if Aguilar was a student there.

Aguilar purchased the shotgun last month at a store in neighboring Montgomery County, McMahon said.

When police arrived at the mall, they found three bodies at the shop on the upper level.

Five other people were hurt in the attack and its aftermath, but only one was hit by gunfire. All were released from hospitals by Saturday evening.

At the time of the shooting, the mall was busy with weekend shoppers and employees.

"There were a lot of people very close to where this happened," Howard County Executive Ken Ulman said.

Police searched the mall with dogs overnight, and stores were to remain closed through Tuesday.

Joan Harding of Elkridge, Md., was shopping with her husband, David, for a tiara for their granddaughter's 18th birthday when she heard something heavy falling, followed by gunshots and people running.

"My husband said, 'Get down!' and the girl that worked in the store said, 'Get in the back,'" Harding said. That is where they hid until police searched the mall and signaled it was safe to leave.

The shooting took place at a shop called Zumiez, which sells skateboards, clothing and accessories. The company's chief executive, Rick Brooks, said employees were being offered counseling.

Police identified the victims as 21-year-old Brianna Benlolo of College Park, Md., and 25-year-old Tyler Johnson of Ellicott City, Md.

Benlolo's grandfather, John Feins, said in a telephone interview from Florida that his granddaughter had a 2-year-old son and that the job at Zumiez was her first since she went back to work after her son's birth.

"She was all excited because she was the manager there," he said.

He said he had spoken with his daughter, Brianna's mother, earlier in the day, but didn't know who the gunman was or whether the person knew his granddaughter.

He described his daughter's family as a military family that had moved frequently and had been in Colorado before moving to Maryland about two years ago. He said his granddaughter was on good terms with her son's father, and they shared custody.

"I mean what can you say? You go to work and make a dollar and you got some idiot coming in and blowing people away," he said.

The mall is at the center of the town, which is a suburb of both Baltimore and Washington.

Tonya Broughton of Silver Spring, Md., was with a friend getting facials when she heard people running and screaming, "There's a shooter! There's a shooter!" she said.

Wearing a gel face mask, she and her friend hid in a Victoria's Secret store.

Laura McKindles of Columbia, who works at a kiosk in the mall, said she heard eight to 10 gunshots, followed by people running and screaming. She ran into the backroom of a perfume store and locked the door.

Allison Cohen, who works at the Lucky Brand Jeans store, said she always felt safe at the mall.

"I truly never thought something like this would ever happen here," Cohen said. "It's really, really shocking."