Police hold a press conference about the arrest of a suspect of the Boston bombings in Watertown of Boston, the United States, April 19, 2013. Suspect of the Boston Marathon bombings, 19-year-old Dzhokhar A. Tsarnaev, was captured on a boat parked on a residential property in Watertown, the state of Massachusetts, on Friday. (Xinhua/Zhang Jun)

Policemen block Franklin street where a suspect of the Boston bombings hid in the Watertown district of Boston, the United States, April 19, 2013. Suspect of the Boston Marathon bombings, 19-year-old Dzhokhar A. Tsarnaev, was captured on a boat parked on a residential property in Watertown, the state of Massachusetts, on Friday. (Xinhua/Zhang Jun)

Policemen block Franklin street where a suspect of the Boston bombings hid in the Watertown district of Boston, the United States, April 19, 2013. Suspect of the Boston Marathon bombings, 19-year-old Dzhokhar A. Tsarnaev, was captured on a boat parked on a residential property in Watertown, the state of Massachusetts, on Friday. (Xinhua/Zhang Jun)

Policemen leave the place where a suspect of the Boston bombings was arrested in the Watertown district of Boston, the United States, April 19, 2013. Suspect of the Boston Marathon bombings, 19-year-old Dzhokhar A. Tsarnaev, was captured on a boat parked on a residential property in Watertown, the state of Massachusetts, on Friday. (Xinhua/Zhang Jun)

An ambulance leaves the place where a suspect of the Boston bombings was arrested in Watertown of Boston, the United States, April 19, 2013. Suspect of the Boston Marathon bombings, 19-year-old Dzhokhar A. Tsarnaev, was captured on a boat parked on a residential property in Watertown, the state of Massachusetts, on Friday. (Xinhua/Zhang Jun)

Residents walk out of their houses after a suspect of the Boston bombings was arrested in Watertown of Boston, the United States, April 19, 2013. Suspect of the Boston Marathon bombings, 19-year-old Dzhokhar A. Tsarnaev, was captured on a boat parked on a residential property in Watertown, the state of Massachusetts, on Friday. (Xinhua/Zhang Jun)

Special policemen leave the place where a suspect of the Boston bombings was arrested in Watertown of Boston, the United States, April 19, 2013. Suspect of the Boston Marathon bombings, 19-year-old Dzhokhar A. Tsarnaev, was captured on a boat parked on a residential property in Watertown, the state of Massachusetts, on Friday. (Xinhua/Zhang Jun)