Police were alerted to reports of gunshots heard and a large group presence in Braintree Road at 6.21pm on September 7.
Officers attended and found the group had dispersed.
A short while later, a suspicious vehicle was seen nearby and police pursued it to Abercorn Gardens, Romford.
One of the occupants discarded items, including two zombie knifes, which were recovered by police.
The car stopped for a second time in Barley Lane, Ilford, with police arresting two 17-year-old boys and a 19-year-old man on suspicion of possession of offensive weapons.
All three males remain in custody.
The boy self-presented to hospital with gunshot wounds that are not believed to be life-threatening or life-changing.
Police enquiries are ongoing.
Anyone with information is asked to contact police on 101 or online quoting CAD 5654/7SEP. Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.
