The chairman of the House Homeland Security Committee is pressing for more information about what happened to bombing suspect Tamerlan Tsarnaev during the six months after he reportedly boarded a Moscow-bound plane last year.

During televised interviews, Rep. Michael McCaul (R-Texas) said the trip could be an indication that Tsarnaev, 26, was trained and radicalized by Chechen rebels, who work “hand in glove” with al Qaeda in Pakistan.