January 2013: Darion Marcus Aguilar begins searching for “mass murder” and “Columbine” on the Internet and seeking information on how to assemble and disassemble shotguns. He also begins a handwritten journal, describing how he wants to kill people, contemplates suicide and rants about his hatred for unspecified groups. One entry released by police warns that he would start killing in hours, but authorities did not reveal when that was written.

April 2013: Aguilar visits a doctor for an unspecified medical issue and tells him that he’s hearing voices. He does not mention having violent thoughts. The doctor later tells authorities that he urged Aguilar to see a psychiatrist, but there’s no evidence he did so. The doctor says he also told Aguilar’s mother, who promised to seek help. Aguilar’s mother tells police she doesn’t recall the conversation.

Dec. 10, 2013: Aguilar buys a pistol-gripped, 28-inch-long, pump action Mossberg 500 12-gauge shotgun from United Gun Shop in Rockville. He also buys two boxes of shells. He returns to the store later with a friend to buy more shells and to ask questions about shooting. Police say he told his friend that he was target-practicing.

Dec. 28, 2013: Aguilar is seen on surveillance video at the Bass Pro Shop at Arundel Mills mall buying additional ammunition.

Jan. 10: Aguilar visits a Home Depot in College Park and buys a common household cleaning solution that could be used to create a makeshift bomb. Surveillance video shows him leaving the store. On the same day, he takes pictures of the gun, ammunition and explosives material in his bedroom. One picture shows the assembled shotgun at 8:21 a.m. A second photo, at 8:24 a.m., shows the gun disassembled.


Violence erupted at a suburban mall in Columbia, Md. on Saturday morning, after a shooter emerged from among weekend shoppers. Police confirmed that three people were left dead, including one believed to be the shooter.

5:15 a.m.: Aguilar leaves his home in College Park.

6:19 a.m.: He visits an ATM at a PNC Bank in Beltsville.

7:31 a.m.: He boards a Metrobus to Burtonsville, the final stop.

9:39 a.m.: Is seen on video alone inside a McDonald’s in Burtonsville, wearing a hooded sweatshirt and the backpack which police believe contained two makeshift explosive devices and the disassembled shotgun.

9:50 a.m.: He leaves Burtonsville in a Barwood taxi he had called.

10:10 a.m.: Surveillance video shows Aguilar being dropped off at the Mall in Columbia, near Sears.

10:16 a.m.: Aguilar is seen going into the mall near the carousel entrance.

10:18 a.m.: He walks near the Zumiez store on the upper level and then is seen taking an escalator down to the food court.

11:01 a.m.: Aguilar takes an escalator back upstairs, enters Zumiez and walks into the dressing room. Police believe that he was waiting until 11:14 a.m. to begin shooting, the same time the Columbine High School shootings started. He puts on a new camouflage shirt, similar to one worn by a Columbine shooter.

11:14 a.m.: Aguilar takes a photo of himself holding a shotgun and uploads it to Tumblr, along with a message saying, “Today is the day.” He steps out and fatally shoots one clerk, then another. He fires another shot across a hallway, hitting a woman in her heel. He fires down into the foot court, narrowly missing others. He then fires through a window at Zumiez, shattering the glass and hitting a mannequin. He walks back into the store and fatally shoots himself in the head.

Sources: Howard County Police Department, interview with owner of gun shop in Rockville.

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