Someone claiming to be his friend has identified him on Twitter. His nationality is still not known, but it may be Somali. There are not many things on Google about the man, who has not been officially identified by the police. Reports and video show him bragging over the murder, praising God for the death of an alleged British soldier.
UPDATE: Photo here.
More info here:
I knew Mujahid had changed, last time I saw him, he had memorized so much Quran & was very strict & precise on his worship & manners
— Abu Nusaybah (@AbuNusaybahUK) May 22, 2013