A man was hit with air pellets while walking through Kettering.
Paul Preece was walking in the Rockingham Road area of Kettering at the start of September when he was hit by a pellet.
Police have been unable to confirm whether the pellet was shot from an airgun or whether a catapult was used.
Mr Preece had to have an operation to remove the object, which lodged itself about an inch deep in his arm.
He had been walking near the convenience store at the junction with Grafton Street.
The father-of two, 43, said: “I was posting a letter then walking back along Rockingham Road.
“I heard this fizz around my head a couple of times.”
He was then hit and was taken to accident and emergency at Kettering General Hospital and was forced to take three days off work.
Mr Preece added: “I’ve got to go back in a few weeks to get the stitches removed. The surgeon said it was lucky it didn’t hit any of my nerves.
“I am a bit wary now. What if it had hit one of my kids?
“I almost put my head down a little bit now when I’m walking. It could have been a lot worse.”
A Northamptonshire Police spokesman confirmed the investigation was ongoing, adding that officers had not made any arrests.
The spokesman said the incident had been reported about 9pm on Tuesday, September 2.
Similar incidents involving objects, possibly small stones, were reported as being catapulted towards Rockingham Road near its junction with William Street the previous day. In those incidents, a man was hit in the leg and a car was struck by one of the objects.
Anyone with information or who saw any suspicious activity in the area has been urged to call police on 101 or Crimestoppers anonymously on 0800 555111.