According to reports, the attacker who sped the car across Westminster bridge outside UK Parliament and killed three persons including a policeman he stabbed has been identified as Khalid Masood. Masood, a 52-year-old British-born man, was once investigated by MI5 intelligence officers over concerns about violent extremism, say reports. Moreover, one of the injured in the attack,  a 75-year-old man, died in hospital taking the death toll to five.