When Adam Lanza stormed into the Sandy Hook Elementary School in Newtown, Conn., on Dec. 14, 2012, opening fire on schoolchildren and sending kindergartners scrambling into closets for protection, American news outlets immediately began asking the desperate question, "Why?"

What made Lanza into a school shooter and mass murderer? Was it his family background, his reported autism, his political viewpoints, even his time spent in homeschooling?

Thoroughly profiling the perpetrator has become the first response of the American media in every shocking crime from Sandy Hook to the Boston Marathon bombing and more.

But almost one year to the date after the Sandy Hook shooting, on Dec. 13, 2013, at the Arapahoe High School in Centennial, Colo., another school shooter opened fire, and this time, the gunman's background was all too quickly swept under the rug.

TRENDING: In the end, the rioters are Obama's army

Most notoriously, the Denver Post discovered in its profiling of shooter Karl Halverson Pierson that fellow students described the 18-year-old gunman as "a very opinionated socialist." Yet by the next day, the Post's editors had scrubbed the word "socialist" from the article, replacing it with merely "very opinionated."

In fact, the first words the article uses to describe Pierson are "outspoken about politics, was a gifted debater and might have been bullied for his beliefs … a dedicated, bright student from a religious family that attends Bible study meetings."

Gone from the Post article was the "socialist" reference, and only much later in the article do readers learn of Pierson's politics, when the Post reports Pierson mocked Republicans on Facebook, writing, "You Republicans are so cute," and posting an image that reads: "The Republican Party: Health Care: Let 'em Die, Climate Change: Let 'em Die, Gun Violence: Let 'em Die, Women's Rights: Let 'em Die, More War: Let 'em Die. Is this really the side you want to be on?"

Furthermore, a quick search for online news articles published the Monday following the Friday shooting revealed more than 2,600 articles profiling one of Pierson's shooting victims, but only two that still sought to dig up information about the shooter's motivations. Neither article, however, mentions Pierson's socialist politics, nor other details revealed by a Wall Street Journal interview with a fellow student who said Pierson "once wore a shirt emblazoned with the letters U.S.S.R. and described himself as a communist."

The Post's Senior Editor for News Lee Ann Colacioppo later offered a defense for scrubbing the nature of Pierson's politics, responding to criticism via Twitter, "We decided not to have another student apply a label to the shooter – a label the student likely didn't even understand."

Several media critics, however, aren't buying Colacioppo's excuse or excusing the mainstream media's sudden apathy about the school shooter's politics.

"If Pierson had been an evangelical Christian or free-market and small-government advocate, we all know that such would be the lead headline in every story about him, along with prominent mention of his shared views with the Republican Party," writes Victor Keith in American Thinker. "But since he was a socialist who hated Republicans, that little tidbit will be buried at the end of any article, if it is mentioned at all."

"The gun angle is powerfully inconvenient for the left, too," notes John Hayward in Human Events, recalling the renewed demand for gun-control laws in the aftermath of Sandy Hook. "The Denver Post coyly relates a student saying Pierson 'had very strong beliefs about gun laws and stuff,' but doesn't bother to inform readers of what those strong beliefs might have been. It falls to the U.K. Daily Mail to tell us that he 'seemingly supported gun control.' It doesn't seem like it would be that difficult to find out exactly where he stood on the issue, seeing as how he was so outspoken, and his stance on gun legislation was so strong. The fact that no media outlets seem interested in clarifying the matter speaks volumes."

What we do understand

Authorities say Pierson, 18, a senior at Arapahoe High School, entered the school about 12:33 p.m. local time on Friday, Dec. 13, armed with a shotgun, a bandolier stocked with ammunition, a machete and three Molotov cocktails.

Students who witnessed the attack say he was searching for the school librarian and debate team coach, Tracy Murphy, whom he had disagreements with and had even threatened earlier.

Pierson fired a random shot down the school hallway, then entered an area where 17-year-old Claire Davis was seated with a friend and shot her at point-blank range. Davis was later taken to the hospital in critical condition and remains in a coma.

Pierson then fired again down the hallway and entered the library where he presumably hoped to find Murphy. Pierson used the Molotov cocktails to start fires in the library, but Murphy left the premises – police say it was an attempt to lure Pierson away from the other students.

Finally, an armed school resource officer approached Pierson, whereupon the student took his own life. The entire attack lasted about 80 seconds.

Most speculation points to Pierson targeting Murphy after a conflict that caused Pierson to stop participating in debate.

"'Revenge' is the word that I chose," Arapahoe County Sheriff Grayson Robinson told reporters. "This is where our initial investigation is taking us. We know that there was some controversy between the student suspect and the teacher."

Further research into Pierson's background and interviews with students have so far revealed little more about possible motive, but quite a bit more about Pierson's mindset.

Senior Chris Davis, 18, no relation to Claire, was among many students trying to make sense of Pierson's shooting rampage the next day.

"He was a weird kid," Davis told CNN. "He's a self-proclaimed communist, just wears Soviet shirts all the time."

Pierson became easily aggravated, "always liked to be right" and didn't like losing, Davis said.

"It seems realistic, now, that he did it," Davis added.

Joe Redmond, who at one time was a co-captain on the debate team with Pierson, told NBC News the gunman had been reading "The Anarchist Cookbook," a 1971 book that includes bomb-making instructions, since his sophomore year and had been sharing it with others.

Redmond echoed the belief that Pierson was targeting his former debate coach, explaining Pierson and Murphy "did not get along, and whatever it was escalated to a death threat."

"Speech and debate was his life, and the fact that he wasn't there crushed him a little bit and made him really tense and angry," Redmond told NBC News.

Other students described Pierson as a smart and sometimes goofy student who often talked about his beliefs during class, sometimes even debating his teachers, the Associated Press reports. They said he elaborated often on his communist-leaning political views.

Fellow student Angie Mock, in the following video, described Pierson as "very proud of being a socialist … very outspoken on his political views."

The Denver Post reports Pierson had been successful in the debate team, even finishing third in a state competition in April and earning a trip to the national competition in Alabama in June.

Redmond told the paper Pierson, who was Arapahoe's sole entrant in the competition, attended the event with Murphy. But somewhere along the line, the coach and student had a falling out. At the start of this school year, Pierson was the extemporaneous captain on the team. By October, his listing as one of the team officers had been removed from the school's website.

Sheriff Robinson told the paper Pierson and Murphy had a conflict in September and Pierson was disciplined. Robinson did not elaborate, saying only that Pierson was not suspended or kicked off the team. Whatever happened, it was not disclosed to the rest of the team.

"It was all very hush-hush," Redmond said.

Yet Redmond says when he invited Pierson to return to the squad, Pierson responded of the debate coach, "I hate him so much that I can't come back."

Murphy has not been available for comment, but the school district released the following statement on his behalf: "Arapahoe High School teacher Tracy Murphy has asked that we share his and his family's concern for all of the victims of this tragedy. Littleton Public Schools, the Arapahoe High School community, and the Tracy Murphy family appreciate the support and kindness received over the last few days. Littleton Public Schools asks that you respect Mr. Murphy's privacy and the privacy of all LPS community members who are grieving."