Transcript for Khalid Masood identified by police as man behind London attack

Next tonight, ISIS has taken responsibility for that terror attack in London. The death toll rising again today. Crowds gathered for vigils. Take a look this evening to remember the lives lost. One of those, an American from Utah, celebrating a milestone anniversary. There with his wife. ABC's Terry Moran reporting from London tonight. Reporter: Tonight we are learning more about the man who attacked the heart of London. Khalid Masood, 52 years old. British-born. Believed to have acted alone, though he was long known to authorities here as an islamist radical. Police now executing raids across the country, arresting eight, and seizing evidence. The investigation centering on the city of Birmingham in the north of England, where Masood was living, and ABC's Alex Marquardt is there. Reporter: This house is Masood's last known address. It was raided overnight by police. One neighbor identified Masood from a picture of the attack, saying he was a Normal family man who like to take care of his garden, but who left abruptly just after Christmas. Reporter: Outside parliament today, where the rampage happened, forensic technicians on their hands and knees, painstakingly searching for evidence. London was a city defiant. Parliament was in session. The Westminster bridge reopened the afternoon. The attacker sped the 800-foot length of this bridge, up on the sidewalk much of the time. Look how narrow it is. His SUV would have taken up most of it. He ran over dozens of people. One woman going into the water. That surveillance video shows the car barrelling on, crashing into the railing, surrounding parliament. Masood then getting out, armed with two knives,charged the main Gates, fatally stabbing a police officer,finally shot down himself as he tried to attack other officers. The murdered police officer, 48-year-old Keith palmer, married and the father of a 5-year-old girl. Also killed, aysha frade, on her way to pick up her daughters from school. And a man taken off life support tonight, and an American, Kirk Cochran, 54 visiting London with his wife, Melissa, celebrating their 25th wedding anniversary, walking along the Westminster bridge. He did live his dream, and not a lot of people get to do that. And Kirk Cochran's wife, Melissa surviving and recovering in a hospital tonight. ISIS has claimed responsibility for this attack. British authorities still describing it though as a lone wolf? Reporter: That's right, Tom. They say while ISIS claims him as a soldier of the islamic state, they say he acted alone, and they are dinging through his long history of radicalization, but they don't believe he has

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