WASHINGTON (AP) — Government officials say Boston Marathon bombing suspect Tamerlan Tsarnaev traveled to Russia last year and returned to the U.S. six months later.

The 26-year-old Tsarnaev died in a police shootout overnight.

The officials spoke on condition of anonymity because they couldn't publicly talk about an investigation in progress. One says that Tsarnaev traveled out of John F. Kennedy International Airport in New York.

Advertisement:

Investigators believe that Tsarneaev and his brother Dzhokhar are responsible for the deadly Boston Marathon terrorist attack. Dzhokhar is still being sought. The ethnic Chechen brothers are from Dagestan, which neighbors Chechnya in southern Russia. They lived near Boston and had been in the U.S. for about a decade, an uncle said.

One official said there are no known ties at this point to Chechen extremist groups.