A man was arrested on Sunday (September 23) and taken to an east London station for questioning.
It comes after a 19-year-old man was gunned down in Walthamstow’s Vallentin Road at around 11pm on Saturday (September 22).
The victim was driven to hospital by friends where he died at around 11.40pm. His family have been informed and a post-mortem examination is due to take place.
Detectives from the Homicide and Major Crime Command are appealing for witnesses to come forward to aid their investigation.
Additional police will be patrolling the Walthamstow area in the coming days and CCTV footage has been obtained by officers for examination.
DCI Paul Healy said: “This was a shocking attack on a young man on a busy Saturday night. “We are keen to hear from anyone who was in the proximity of Shernhall Street, Wood Street, Upper Walthamstow Road or Vallentin Road, E17, between 10pm and 11.30pm. “The perpetrators need to be found and the firearm taken off the streets. “If you have footage related to the incident, including dash-cam footage, we need to hear from you. “Equally if you were a witness and are yet to come forward, I would urge you to get in touch.
A crime scene remains in place and police will be speaking to those in the area.
Extra police will be in the area and a number of enquiries including the recovery of local CCTV footage and forensic analysis are ongoing.