TIPP CITY, Ohio - US President Bush said on Thursday that mass shootings are a reminder that people must be willing to raise a red flag about others' disturbing behavior.

US President Bush speaks at Tippecanoe High School gymnasium Thursday, April 19, 2007 in Tipp City, Ohio. [AP]

"One of the lessons of these tragedies is to make sure that when people see somebody or know somebody who is exhibiting abnormal behavior, you do something about it, to suggest that somebody take a look," the president said during an appearance at a high school here.

His war on terror speech came after a moment of silence for the victims of the Monday shootings at Virginia Tech in which 33 people, including the shooter, died.

In a question-and-answer session, the president was asked by a student what he thought should be done to ensure safety in schools.

He said he didn't want to draw conclusions from the Virginia case because "they're still digging out the facts." But he suggested that concerns about privacy violations, while understandable, may be preventing people from taking needed action.

Gunman Cho Seung-Hui had been accused of sending unwanted messages to two women. He was taken to a psychiatric hospital on a magistrate's orders and was pronounced a danger to himself, but was released for outpatient treatment. Also, Cho's twisted, violence-filled writings and menacing, uncommunicative demeanor had disturbed professors and students so much that he was removed from one English class and was repeatedly urged to get counseling. A video rant Cho mailed to NBC in the middle of his Virginia Tech rampage only added to the disturbing psychological portrait.

White House spokeswoman Dana Perino said she did not know whether Bush had seen any of the video. But it was clear he was aware of it.

"If you are a parent and your child is, you know, doing strange things on the Internet, pay attention to it and not be afraid to ask for help and not be afraid to say `I am concerned about what I am seeing," Bush said. "I think it's very important for us not to comment until it's all said and done, but that other cases there have been warning signals - that if an adult for example had taken the signals seriously, perhaps tragedy could have been avoided."

Bush said the reeling community in Blacksburg should take heart from its support in the rest of the country.

"It really speaks to the strength of this country, doesn't it, that total strangers here in Ohio are willing to hold up people in Virginia in prayer?" he said.