Three people were found with gunshot wounds. One victim, a 42-year-old woman, died at the scene.
The two others - a 20-year-old man and a 16-year-old boy - were taken to hospital where their conditions are being assessed, the Met said.
No arrests have been made.
Speaking outside a police cordon on Wednesday morning, a neighbours said they heard the daughter of the victim screaming following the incident.
She added that three shots were fired and she knew the woman who was killed but was unsure of the identities of the 20-year-old man and 16-year-old boy who were injured in the incident.
“This shocking incident has resulted in the death of a woman and my thoughts are with her family at this incredibly difficult time. My thoughts are also with the two people who have been taken to hospital,” Detective Superintendent Vicky Tunstall, from the local policing team in Hackney, said.
She added: “I do not underestimate the impact this incident will have on people in Hackney and I understand the community will want answers about what has happened this evening. We will share further information as our investigation progresses.
“Gun crime has no place on the streets of London and we will do all we can to bring whoever is responsible for this despicable crime to justice.”
Anyone who witnessed the shooting, or has information about what happened, is asked to call 101 quoting CAD 5811/05Dec.