hostages identified. a senior intelligence official saying he is mohammed emwazi. he is a native of kuwait, a college graduate who grew up in this neighborhood in west london. >> such a beautiful young man. really it is hard to imagine the trajectory. >> reporter: those who knew him well say before he left for syria three years ago where he later joined isis, emwazi had grown frustrated with the british government. the "washington post" reporter who uncovered his identity was told mi5 questioned emwazi and tried to recruit him. >> they had his dna, fingerprints, had taken pictures of him. they were watching him. what happened? did he fall off their radar? >> reporter: u.s. and british intelligence officials have known who was behind the mask for months but still have not commenting. as the hunt for emwazi continues the family of one of his victims, american journalist