U.S. Vice President Joe Biden is criticizing the two Boston Marathon bombing suspects as perverted and cowardly.
Biden spoke Wednesday in Boston at a memorial service for a university police officer who authorities say was gunned down by suspects Tamerlan and Dzhokhar Tsarnaev, three days after the bombings.
The vice president questioned why anyone acts to terrorize innocent people.
"Why, whether it’s al-Qaida central ... or two twisted, perverted, cowardly, knock-off jihadists here in Boston. Why do they do what they do?," he asked.
Several thousand mourners gathered at the Massachusetts Institute of Technology
to remember the slain policeman, Sean Collier. Biden said the United States must keep its values in the face of threats from terrorists.
"The only way they can gain ground is to instill fear that causes us to jettison our values, our way of life, for us to change," he said. "The moment we change, the moment we look inward, the moment we get into a crouch in a defensive, that’s the moment when they win."
Meanwhile, U.S. investigators have questioned the parents of the two suspects in the Russian republic of Dagestan, as they try to determine what might have influenced the sons in the months before the attack.
U.S. authorities, working with Russian security forces, interviewed the parents Tuesday night and called back the mother, Zubeidat Tsarnaev, for more questioning on Wednesday.
The investigators are particularly interested in any contacts the elder brother, Tamerlan Tsarnaev, might have had with Islamic extremists during a six-month visit to Dagestan and Chechnya last year.
U.S. lawmakers discussed the same trip Tuesday as they raised concerns about the sharing of intelligence among federal law enforcement agencies. Senator Lindsey Graham said the FBI told him it was not aware at the time of Tamerlan Tsarnaev's trip to Russia.
Tamerlan Tsarnaev, who was 26, died after a shootout with police last Thursday, while his younger brother Dzhokhar was captured a day later. The 19-year-old Dzhokhar has been charged with using a weapon of mass destruction. He is in federal custody in a Boston hospital.
The brothers allegedly set off two bombs alongside the Boston Marathon course, killing three people and injuring 264. At least 14 of the wounded lost legs in the blasts.
Boston authorities on Wednesday reopened Boylston Street to the public. It is the city thoroughfare where the explosions occurred.