Khalid Masood, 52, was seen in a new build Olympic village apartment just weeks before he ploughed into pedestrians on Westminster Bridge, killing four.
Today a mum-of-two said she and her 14-year-old brother had seen Masood several weeks ago.
It comes after cops spent hours turfing through the apartment and removing evidence before leaving at around midnight.
He was really nice and polite as well, he was very pleasant. I'm very shocked
Vera Amade, neighbour
Vera Amade, 21, a mum-of-two said: "My brother saw him a few times quite recently in the last few weeks.
"It was definitely him, the woman has two kids, one of the daughters has just had a baby.
"They all live in the same flat. She was quite polite, there was nothing bad to say about her.
London terrorist Khalid Masood's neighbours described the shock they felt
"He was really nice and polite as well, he was very pleasant. I'm very shocked.
"We were watching it on TV last night and trying to figure out if it was definitely him and it is.
London terror attack: Latest pictures Fri, March 24, 2017
4 dead and 40 injured in London terror attack
PA 1 of 44
Get Quotes on Home Insurance
Conservative MP Tobias Ellwood (centre) helps emergency services attend to a police officer outside the Palace of Westminster, London
Neighbours were trying to figure out if the killer was in fact the person they knew
"He was always dressed in a suit, I don't know what he did for a living. He used to come back from work at about five or six.
"We can't believe it, it's shocking."