Even the experts were stunned.

The cause of yesterday's attack on the World Trade Center in New York City and the Pentagon in Washington, D.C. left many Penn State researchers puzzled.

"There is a real statement here, which tends to align with other methods in terrorist attacks," said Dr. Sharon Love, assistant professor of criminal justice and sociology at Penn State Altoona.

Love was in Oklahoma City when the Alfred P. Murrah Federal Building was bombed in 1995.

"I think there are a lot of parallels in the way the nation is responding to this disaster and to the way in which they responded to Oklahoma City," Love said.

She also feels that while this may have been a terrorist attack, it is different from what happened in Oklahoma.

"There are also a lot of markers that would lead me to believe this is an international terrorist attack as opposed to a national attack like Oklahoma City," Love said.

Though she witnessed the horror of this type of tragedy before, Love is optimistic that people will pull together.

Dr. James Ruiz, assistant professor of criminology at Penn State Harrisburg, agreed with Love.

Ruiz, however, said he is concerned with American's rights and how they are affected by these attacks.

"We must look at our rights and how badly our civil liberties can suffer at a time like this," Ruiz said.

These sorts of attacks can be an infringement on civil liberties, Ruiz said. He feels that Americans' rights, specifically the search and seizure clause of the Fourth Amendment, are now in jeopardy, as it may become customary for airport officials to search passenger belongings.

He also is concerned with airport security and what measures will be taken with passengers and air travel.

Ruiz also questioned the intelligence efforts of the U.S. government.

"This also shows how totally ineffective our intelligence bureau is. We didn't see this coming?" Ruiz said. "There are intelligence officers everywhere. How did this get by them?"

Arthur K. Anderson, professor emeritus of architecture, was also shocked by yesterday's attacks on the Trade Center.

"We've got a lot of pictures of the World Trade Center and they are now history because I can't imagine anyone rebuilding something like this," Anderson said.

Anderson also is concerned about the structural fragility of high-rise buildings and their vulnerability.

"I think what we witnessed today was essentially the death of the high-rise building," Anderson said.

Ted Krauthammer, director of the Protective Technology Center and professor of civil engineering at Penn State, currently is working on research that would make these buildings more resistant to terrorist attacks.

"It's very traumatic, very sad that we have incidents where people are targeting civilian buildings," Krauthammer said.

The Protective Technology Center, created last year through a grant from the U.S. Army, is based at Penn State with additional research being conducted at Mississippi State and Jackson State universities. Congress authorized funding for the project in response to terrorist bombings at U.S. embassies in Kenya and Tanzania last year.

The center's research is directly involved with strengthening buildings against terrorist attacks.

Steps were already taken to strengthen the Trade Center after terrorists set off a car bomb in the parking garage in 1993, Krauthammer said.

"This might be why the perpetrators used an airplane, because the building was most likely strengthened against a car bomb incident," Krauthammer said.

The Associated Press and Collegian staff writer Christina Parris contributed to this report.