The House Homeland Security Committee began the first of several hearings Thursday looking into what happened before and after April's Boston Marathon bombings.
Lawmakers want know what signs may have been missed and what can be done to make sure such a tragedy never happens again.
"Anyone who thinks they can execute an attack on this country and change our way of life greatly underestimates our spirit and resolve," Rep. Michael McCaul, R-Texas, said.
Right off the bat, new revelation showed a breakdown in intelligence sharing.
Boston Police Commissioner Edward Davis said officials didn't know until three days after the bombing that the older bombing suspect, Tamerlan Tsarnaev, had been flagged by the intelligence community.
"My fear is that Boston bombers may have succeeded because our system failed. We can and must do better," McCaul said.
In 2011, Russia asked the FBI and CIA to look into Tsarnaev's possible ties to radical Islamists. U.S. investigators found nothing and closed its case. Again, that piece of information was never shared with the Boston police.
"Would you like to have known that?" McCaul asked Davis.
"In hindsight, yes," the commissioner replied.
Equally of concern to lawmakers is the emerging narrative from the White House. The Obama administration continues to downplay the threat posed by radical Islamists.
"From the attack at Fort Hood to the tragedy of Benghazi, the Boston bombings are our most recent reminders that we call terrorism really for what it is in order to confront it," McCaul said.
Former Sen. Joe Lieberman, I-Conn., says violent Islamic extremism is alive and well and the government needs to do more to counter it.
"I believe, though it would not have been easy, we could have stopped the terrorist attack in Boston," Lieberman said.
In prepared remarks, Davis called for tighter security at public events, including more undercover officers, technology and surveillance cameras.
Nevertheless, Davis added he does not support actions that would give the nation a "police state mentality."
"I do not endorse actions that move Boston and our nation into a police state mentality with surveillance cameras attached to every light pole in the city," Davis said. "We do not and cannot live in a protective enclosure because of the actions of extremists who seek to disrupt our way of life."
Cameras from a nearby restaurant helped identify the two suspects in the Boston Marathon bombing.
"Images from cameras do not lie. They do not forget," Davis said. "They can be viewed by a jury as evidence of what occurred. These efforts are not intended to chill or stifle free speech, but rather to protect the integrity and freedom of that speech and to protect the rights of victims and suspects alike."