According to Doug Miller of Denver's Alcohol, Tobacco and Firearms licensing division, it probably wasn't that difficult.
"Unfortunately, as long as somebody wants to sell a gun, anybody can buy one," Miller said. "People are supposed to comply by regulations, but that doesn't always happen."
In the state of Colorado, no permit is required to purchase a rifle, shotgun or handgun, although a person must be at least 18 to buy a shotgun or rifle and 21 to buy a handgun. Harris was 18 and Klebold was 17 when they shot 12 students, one teacher and themselves on Tuesday.
ATF officials are now tracing the purchase of the two shotguns, one 9mm semi-automatic rifle and one semi-automatic pistol that the suspects used to gun down their classmates. Steve Davis, the Jefferson County sheriff's deputy has stated that the two shotguns have been difficult to trace since both weapons appear to be very old models that date possibly as far back as the 1960s.
Davis said the original purchases of the two handguns have been traced, although he declined to say where and when the guns where purchased. A Wall Street Journal article reported Friday that both weapons were originally bought in the Denver area.
Davis stressed, however, that learning where the weapons were originally purchased may not be much help to investigators. "These weapons could have changed hands many times before getting to the suspects," he said.
Since the shooting, many have called for tighter restrictions on the sales and licensing of handguns in the state of Colorado. A highly contentious bill to relax state legislation for concealed weapons was dropped Wednesday when the bill's sponsors were overwhelmed with phone calls to abandon the effort.
And the mother of two Columbine students who were traumatized, but not physically injured in Tuesday's rampage, said she is "very angry" over the National Rifle Association's decision to go ahead with its annual meeting in Denver this week. NRA president Charlton Heston has trimmed back the group's scheduled conference to one business meeting, but has refused to cancel the conference altogether.
"They should put it off or hold it somewhere else. These kids got a hold of a lot of weaponry, and to me, it's somehow connected with the NRA message," said Anne Mohr, whose son, Doug, is in shock and has not left the house since Tuesday night.
Denver Mayor Wellington Webb has repeatedly urged the NRA to cancel its conference. Denver City Council President Allegra Haynes has also called for the meetings to be scrapped, saying "We don't want them here." Even the owner of Littleton Pawn Bank, a gun shop not far from Columbine High School, feels it's inappropriate for the NRA to go ahead with its meetings.
"It's not a good time to talk about guns," said the owner, Brian, who declined to give his last name. "It's not politically correct right now."
But Steve Schweitzberger, a parent who waited one terrifying hour on Tuesday before learning his daughter was OK, believes it's irrelevant to focus on issue of gun control. He points out that the two suspects also used at least 31 homemade bombs to terrorize the school.
"How do you prevent that? Do you ban gasoline?" he said. "There are so many guns in this country, I wouldn't want to be unarmed."
Instead, Schweitzberger believes officials need to step up security in the schools. Jefferson County Second Sheriff John Donoway also believes that increased security could help solve the problem. Donoway was director of security for schools in the area for 12 years and said he has long contended that security at area schools is insufficient.
"Security in these buildings is kind of an either or thing," he said. "You either have it or you don't. We don't — it's that simple."
Marilyn Saltzman, a spokesperson for Jefferson County Schools said on Wednesday that security at all Jefferson County schools has increased since the shooting. Many have stressed, however, that factors like gun control and security are only secondary to the psychological and social conditions that drove Harris and Klebold to act so savagely.
"It's how we raise our children and what we expose them to in our society," said Michael Skoor, a Lutheran pastor who came to Littleton Wednesday to read the growing piles of memorials for Tuesday's victims. "For the two young men, it seems this was just a game for them. That's the sign of some very deep problems in our society."