The Russian passenger plane that crashed in Egypt last month was brought down by a homemade bomb placed on board in a "terrorist" act, the head of Russia's FSB security service told President Vladimir Putin on Tuesday. "According to our experts, a homemade explosive device equivalent to 1 kilogram of TNT went off on board, which caused the plane to break up in the air, which explains why the fuselage was scattered over such a large territory," Alexander Bortnikov said. "I can certainly say that this was a terrorist act." All 224 people on board, most of them Russian tourists, were killed in the Oct. 31 crash.
Putin vowed to hunt down those responsible for the attack. "There's no statute of limitations for this, we need to know all of their names," he said. "We're going to look for them everywhere wherever they are hiding. We will find them in any place on Earth and punish them." ISIS has claimed responsibility for bringing the Russian plane down in written statements, as well as in video and audio messages posted on the Internet following the crash. It said the attack was retaliation for Russia's air campaign against ISIS—and other groups—in Syria. The group warned Putin that they would also target him "at home" but did not offer any details to back its claim. (Read more Egypt stories.)