A man "armed with knives and making threats to kill" was shot by police after stabbing an officer.
The 28-year-old is in a life-threatening condition following the shooting, which happened after reports of a "domestic incident" in Hackney, east London, on Tuesday night.
The wounded officer was taken to hospital with injuries not thought to be serious.
The Independent Office for Police Conduct is investigating.
The Met said they were called to Knights Close in Lower Clapton at 21:43 GMT.
On Wednesday, a spokesman said the man remains in a life-threatening condition in an east London hospital.