The truth takes time.

What happened? Answering that alone could take months. Finding a full answer to the question “Why?” will be harder still, if it ever comes at all.

Dave Cullen, a journalist and author of the award-winning book “Columbine,” is a truth seeker, but one who depends on patience along with diligence.

His nonfiction masterpiece about the killings at Colorado’s Columbine High School — where on April 20, 1999, two shooters killed 12 students, a teacher and themselves — wasn’t published until a decade later, in 2009.

Cullen, 53, is cautious about reports that come in the immediate aftermath of horrific events. As he learned in writing a book that corrected many misconceptions about Columbine, the truth can be far more complex and nuanced than a first-day sound bite.

Since shots rang out Friday at Marysville Pilchuck High School, Cullen has appeared on CNN and other national news outlets. “Unfortunately,” he said in a phone interview Saturday, he is now a go-to expert in school shootings.

From New York, where he lives, Cullen has closely followed the Marysville coverage. At times Friday, there was little information that didn’t originate from social media or conversations with students fresh from a shocking situation.

“It will take quite a while to sort out what was going on, what drove the kid — if we ever know,” Cullen said.

After what he learned investigating “Columbine,” Cullen has reason to be cautious about how people perceive what they experience. And he said using social media to characterize the Marysville shooter may only offer a slice of reality, not a full picture.

Much has been aired and written about the shooter’s angry or emotional comments on Twitter.

“Be very, very careful about the cherry-picked quote,” Cullen said. He recalled that years after the Columbine shootings, he was seeing one quote from gunman Eric Harris’ journal being spouted as if it were “proof of x, y or z.” It was actually counter to what he learned about the massacre mastermind.

The Marysville Pilchuck shooter’s comments on Twitter “may or may not be indicative overall of the psyche, personality or mind of a kid,” he said. Odds are slim to none that one tweet can explain a tragedy. “Kids say ridiculous things sometimes,” he said.

Having seen the Marysville Pilchuck shooter’s Twitter account, Cullen said “that is what he represented himself to be. It’s part of the truth, a version of the truth, what he chose to let outside to the world.” He puts more credence in private diaries or video statements made by shooters than in social media posts.

With Columbine, Cullen said, it took seven months before the public learned, through a court hearing, that the gunmen had made what became known as “basement tapes.”

Through dogged reporting that took years, Cullen debunked many of the early notions about the Columbine attacks. Killers Harris and Dylan Klebold weren’t outcast members of some “Trench Coat Mafia,” although they used coats to hide guns that dreadful day. They were both good students, and had worked at a pizza restaurant. Klebold had been accepted to the University of Arizona. The headline on The New York Times review of Cullen’s book was “The End of the Trench Coat Mafia.”

Witnesses can simply be wrong. Memories, especially after traumatic events, are often unreliable. “No one does it intentionally, they hear it from someone else,” Cullen said.

Columbine’s principal thought the gunmen were behind him because a shot fired down a hallway hit a glass trophy case and that sound was behind him, Cullen said.

Hearing reports that in Marysville law enforcement interviewed many students right after the incident, Cullen said that’s a big step forward from what happened in Colorado. “Most people will speculate what they don’t know,” he said. “They start speculating from what other witnesses are saying, and are influenced by that.”

Truth takes time, and so does healing.

Cullen has revisited people who lived through the tragedy. After more than 10 years, one mother told him that when you lose a child, the pain always feels recent.

One blunder he saw in Colorado was a banner headline in a Denver newspaper, the second day after the killings.

“Healing Begins.”

Healing had not begun. “It was drastically premature,” Cullen said.

I understand the wishful thinking. If only a community’s compassion could make the pain go away.

Julie Muhlstein: 425-339-3460; jmuhlstein@heraldnet.com.