Officers were called to an address in Kerry Drive, Upminster, on Friday evening and found two people suffering injuries.
A man, believed to be in his 40s, had cuts to his head and police said they were not sure if his injuries were caused by the firearm discharge.
Detectives are investigating a shooting incident in Upminster in which a child was injured https://t.co/UKzliVmoHk
— Havering MPS. #StayAtHomeSaveLives (@MPSHavering) May 1, 2020
The condition of the man and the boy is not known, Scotland Yard added.
Police said: “A number of suspects had made off prior to the arrival of police. A police helicopter also assisted officers in searches, however there has been no arrest at this stage.”
Any witnesses to the incident, which took place at around 9:30pm, are asked to call police on 101 quoting ref 7285/01may.