It has emerged the 24-year-old woman who was fatally shot in Kilburn on Saturday was a nursery teacher.
Sabrina Moss, who had a four-year-old son, was on a night out celebrating her birthday when she was killed.
Police have now arrested a second man in connection with her murder.
Another woman, who was also shot, is in a stable condition in hospital.
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Pictures of today's events unfolding following a major security incident at the Houses of Parliament.
At least two people have died after a knifeman brought terror to the heart of Westminster.
The Cobra committee brings together government ministers with senior officials of the emergency services and security agencies.