Congressman Peter King (R-N.Y.) said that in the aftermath of the London terror attack, better or more routine surveillance of certain individuals could prove to be a good preventative measure.

King, a member of the Homeland Security Committee said that attackers like Khalid Masood in London, or the Boston bombers "act out and seems spontaneous."

But, he added that it is often later discovered that those same people were under investigation in one form or another at one time.

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Maria Bartiromo said Masood, who was identified as a potential extremist in 2010 according to the Guardian, visited Saudi Arabia three times in the past few years to teach English there.

"Where there's smoke there's fire, but in a democratic society, you can't be arresting people on suspicion," King said, adding that conducting routine surveillance after a formal investigation has ended is the key.

He said that law enforcement could have asked whether Masood was in contact with any questionable individuals in Saudi Arabia at the time.

Or, King said, authorities could have questioned Masood's neighbors to try to get a sense of whether he had been radicalized or undergone a "behavioral change."

In the United States, he pointed to several preventative measures law enforcement took in the wake of several terror attacks using vehicles.

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