Harris, left, and Klebold RELATED AUDIO A teacher in the library talks with 911 as shots are fired in the background. AIFF or WAV (349 K/30 sec. audio) RELATED VIDEO CNN's Martin Savidge reports from Littleton, Colorado, on the day's events (April 25) Real 28K 80K Windows Media 28K 80K CNN's Martin Savidge reviews new evidence, including shooter's diary, as community eulogizes one of the victims (April 24) Real 28K 80K Windows Media 28K 80K CNN's Aram Roston looks at liability of parents when their children commit crimes (April 24) Real 28K 80K Windows Media 28K 80K To view the latest video streams on the Littleton school shooting, use the arrow buttons below to scroll through the video gallery.        Windows Media Real        28 K 80 K INTERACTIVE Columbine Memorial See more scenes from the shooting Audio and Images Interactive Map: Recent school shootings in the U.S.  ALSO Fatalities at Columbine High  MESSAGE BOARD Colorado school shooting  SPECIAL SECTION Are schools safe?  Address for letters, cards for Columbine High School Messages for Columbine Communications Services Jefferson County Public Schools P.O. Box 4001 Golden, CO 80401-0001 Weapons found during the investigation: One 9 mm semi-automatic pistol One 9 mm semi-automatic rifle Two sawed-off 12-gauge shotguns More than 30 homemade explosives, some with shrapnel

Police: 'Trenchcoat Mafia' members advised by lawyers

In this story: Possible gun show connection 'We loved as much as we knew how to' Outsider teen clique dislikes media portrayal RELATED STORIES, SITES

LITTLETON, Colorado (CNN) -- The parents of two students who carried out a massacre at their Denver area high school could face criminal charges if the evidence warrants such action, Colorado and federal officials said Sunday.

"I think that perhaps charges will be filed and certainly should be filed," said Gov. Bill Owens on Sunday, the day after investigators announced they found evidence of the massacre's planning in the bedroom of one of the assailants.

Investigators "found in one of the gunmen's homes clear evidence out, sitting in the room, of what was about to happen," Owens said on "Fox News Sunday." He did not say specifically with what the parents could be charged.

U.S. Attorney General Janet Reno said Sunday that the authorities would try to establish what the parents of the two youthful perpetrators knew of their sons' intentions.

"It is important that we identify who is responsible for them having guns, what the parents knew or should have known, and take appropriate steps," Reno said Sunday on NBC's "Meet the Press."

Possible gun show connection

A source at the Federal Bureau of Alcohol, Tobacco and Firearms said Sunday he thinks there is a "gun show connection" to the weapons used in the attack.

Investigators previously have said that two guns used in the attack were purchased from two licensed dealers by different people. Neither purchaser had links to the suspected gunmen.

Since Tuesday's massacre at Columbine High School in Littleton, an affluent suburb southwest of Denver, parents, teachers and others have asked how Eric Harris, 18, and Dylan Klebold, 17, could amass such a large arsenal of guns and bombs without the knowledge of their parents.

The two students killed 12 classmates and one teacher in a hail of bullets and pipe bombs before taking their own lives.

Jefferson County Sheriff said Saturday that evidence of the arsenal was in plain view in the home of one of the two teens.

"A lot of this stuff was clearly visible, and the parents should have known," Stone said. "I think parents should be accountable for their kids' actions."

'We loved as much as we knew how to'

What the parents did know and when they knew it remains a mystery. They have said nothing beyond written statements, including one Saturday from the Klebolds, saying they held a private service for their son "who we loved as much as we knew how to love a child."

But Rick Kornfield, the Klebolds' attorney, told the Denver Post that the sheriff's Saturday statements surprised him.

"I think that with an investigation that's ongoing that includes over 100 federal and local agents, that it's inappropriate for law enforcement to start assessing blame in the middle of an investigation," he said.

Mark Pautler, chief deputy district attorney for Jefferson County, told CNN on Sunday he doubted charges would be brought against the parents.

"At this time, with what we know, I don't think so," he said. "But we have got a fair amount of information from the homes of both Harris and Klebold. We are looking at that."

Friends of the Klebolds describe them as caring, attentive parents.

"This is a conscientious, normal family that's done everything right. This came as a bolt out of the blue," said Michael Briand, an associate of Mrs. Klebold.

Investigators Saturday said they recovered a diary written by one of the gunmen that indicated the attack had been planned for a year. It contained a detailed map of the school, notes of ideal times to find large groups of people, and chilling references to Nazi Germany's Adolf Hitler, whose birthday coincided with the rampage.

The diary, phone records and e-mail all provided new leads into possible co-conspirators, authorities said. None has been identified yet, although investigators say they suspect the two youths could not have acted alone.

Outsider teen clique dislikes media portrayal

Police have spoken to a number of people in addition to the parents of the gunmen. But an official at the Jefferson County Sheriff's office said no arrests were imminent.

Attorneys have advised at least three members of the "Trenchcoat Mafia," CNN has learned.

Members of the group of self-described high school outsiders, which reportedly included the gunmen, expressed concern with how the media has portrayed them since Tuesday's attack. They claim the two shooters were on the fringe of the group.

Jefferson County Sheriff's spokesman Steve Davis said Saturday that a few people questioned by his department had retained counsel.

"That may be because of the nature of questions that they are being asked," he said. "That's the only thing I can figure out. If these people who are being questioned by our people feel because of those types of questions that are being asked that they want an attorney to advise them, that's up to them."

Many investigators continued to work on the case Sunday, despite officially receiving the day off. Others attended an outdoor memorial service at a Littleton shopping center that drew almost 100,000 people, including Vice President Al Gore and singer Amy Grant.

Correspondent Martin Savidge and Associated Press contributed to this report.