News that the suspects in the Boston Marathon bombing were from Chechnya fits in with other clues that indicate the attack had some level of foreign involvement.
"That would explain the pressure cooker bombs," says Paul Fennewald, a retired FBI bomb technician. New photo evidence shows the bombers used a nut and bolt configuration to attach the blasting cap to the lid of a pressure cooker packed with explosives.
Tamerlan Tsarnaev died during a police shootout early Friday. Police continue to look for his brother, Dzhokhar A. Tsarnaev, 19. Reports indicate the pair came to America several years ago and were living in the Boston area.
"We don't see those types of bombs in this part of the country built by domestic criminals," he says. "That's more of a technique that's taught in some of these terrorist training camps overseas."
It makes sense that the two suspects would have had training overseas, or access to training materials that are foreign-based.
This now leaves American investigators wondering why two Chechen immigrants would want to target America. Al-Qaida has influence in the predominantly Muslim state in Russia. Most of the high profile attacks carried out by Chechens have been against Russian targets, according to a primer from the Council on Foreign Relations.
Now the FBI and other investigators must turn to their Russian counterparts to learn more about the bombers' motivations. A legal attaché already based in Moscow or elsewhere in Russia is likely now reaching out to the Federal Security Service of the Russian Federation (FSB).
"They're usually cooperative to a certain extent," says Fennewald, who worked with FSB on training exercises in the late 1990s. "They're going to be cooperative on something like this."
Geo-politics rarely influences a joint investigation of this magnitude, he adds, particularly for such a high profile case. The investigative agencies will likely team up to determine if Monday's attack is part of a bigger plot. Just because the brothers were Chechens doesn't preclude the possibility they had outside influences, Fennewald says.
But he adds that investigators must keep an open mind, particularly for such a charged incident: "Don't start looking for answers you want to find, and unconsciously tune out answers coming forward in your investigation."