Witnesses say gunshots were fired by a gang attacking two teenagers after a row outside McDonalds in Kingston, Milton Keynes.
The victims, an 18-year-old man and a 17-year-old boy, were also assaulted with a hammer.
The pair were walking from the Kingston Centre to Kingston Library along Winchester Circle at 4.30pm on Friday.
They were chased by group of four males - two of them aged about 16 - to the nearby underpass and assaulted with the hammer, causing them head injuries.
“Witnesses believe that a firearm was discharged by one of the offenders, but no-one received any firearms injuries,” said a police spokesman.
Police ask witnesses or anybody with phone or dashcam footage to call 101 quoting reference 43190140591.