(CNN) -- Police say a young man who went on a rampage at a shopping mall in Columbia, Maryland, was so obsessed with the April 1999 massacre at Columbine High School that he dressed up in an outfit reminiscent of those shooters and took a picture of himself.
The shooter, 19-year-old Darion Marcus Aguilar, uploaded the picture of himself dressed in cargo pants and boots to the social networking web site Tumblr before the incident, police said Wednesday.
The photo was taken in the dressing room of the The Mall in Columbia store where Aguilar would commit his crimes.
In late January, Aguilar fatally shot Brianna Benlolo, 21, and Tyler Johnson, 25, and injured a third person before turning the gun on himself.
Police declined to release the photo, saying they believe Aguilar took it to gain notoriety and they won't honor that desire.
Howard County Police Chief Bill McMahon said a message accompanying the picture read, in part; "I had to do this."
A police statement said Aguilar's account has been deactivated by Tumblr.
Police verified previous reports that the shooter and the victims, one of whom worked at the skateboard apparel shop, were not acquainted.
What was made clear from the latest release of information about the case was that police believe Aguilar had studied the Columbine shooting and seemed to be trying to mimic what occurred there.
"Aguilar's weapon, attire, backpack containing explosives and method of suicide were all similar to those used in the Columbine incident, said a Howard County police statement.
On April 20, 1999, two Columbine students, Dylan Klebold and Eric Harris, killed 12 of their classmates, a teacher and then themselves. The school is in Littleton, Colorado.
McMahon said police have learned Aguilar began using the Internet last year to search for information about mass shootings in malls and schools, gun laws and explosive techniques. He even downloaded a video game allowing players to act as one of the shooters from that day.
Juxtaposed with those searches were inquiries about mental illness and visits to sites about suicide prevention.
McMahon said Aguilar also sought help from his regular doctor because he said he was hearing voices. The doctor said he referred Aguilar to a psychiatrist, but it doesn't seem he ever made an appointment.
The doctor told police Aguilar said those voices were non-violent and didn't direct him to do anything, authorities said.
In December 2013, Aguilar purchased a shotgun at a shop just outside Washington, D.C. He was there with a friend, but police said the friend had no suspicions and no knowledge of Aguilar's future plans. Aguilar told his friend he was buying the gun for target practice.
Police also recovered a journal which they said ultimately did not shed a lot of light on Aguilar's motives, but did give them some insight into his disturbed mind.
In one entry, Aguilar wrote, "I (sic) going to *expletive* kill you all in a couple of hours I'm anxious, I hate you all so much you are pathetic pieces of *expletive* who deserve to die. worthless you are all *expletive* worthless. Everything seems fake. I think that I may already be dead."
Police said Aguilar fired a total of nine rounds, but came into the store with 54.
"Frankly, we're fortunate he took his own life rather than to run down the hallway and chase victims as they were leaving," McMahon told reporters.
In the end, McMahon said, it's clear Aguilar thought he was suffering from a mental illness but was afraid to even tell his own mother. McMahon said he believes the discussion on mental health treatment must continue.
"Nobody saw this coming," McMahon said. "He was a young man that didn't garner much attention to himself."
CNN's Joe Johns and Stacey Samuel contributed to this report.