A 21-year-old woman died when she was hit by a police car responding to a 999 call.
The pedestrian was hit by the marked vehicle on Forest Road, Walthamstow, east London, at 23:45 GMT on Tuesday.
Officers stopped and tried to help the woman, but she was pronounced dead at the scene when paramedics arrived, the Met said.
The YMCA St Paul’s Group confirmed the woman had been a resident of its accommodation in Walthamstow.
It said it was “shocked and saddened” by her death.
Police are trying to trace her next of kin, who are thought to live outside the UK.
The car had been responding to reports of a man threatening members of the public, Scotland Yard said.
By the time officers arrived the man had left the scene.
At The Scene: Thomas MacKintosh, BBC London
Forest Road reopened shortly after 09:00 this morning and traffic has been flowing through like it would on any morning.
The remnants of blue and red police tape attached to a few lampposts are the only sign of what happened shortly before midnight.
Residents at the YMCA, where she was staying, believe she was Eritrean.
They described seeing people looking visibly upset and crying this morning during breakfast.
One resident told me that the situation many of the residents living here are in means that they become close friends which is why so many are shocked and saddened.
The Met said it had referred itself to the Independent Office for Police Conduct (IOPC), and informed its own Directorate of Professional Standards.
Walthamstow MP Stella Creasy said the death was “terrible news”.
Forest Road was closed to traffic but has since reopened.