Police were called to a school after a pupil posed with an AK-47 on Facebook in the wake of the Paris attacks.
The smiling student, aged 13 or 14, is seen holding the machine gun with his finger on the trigger on his profile photo understood to have been taken while on a visit to Pakistan earlier this year.
It was seen by teachers at Royton and Crompton School in Oldham, Greater Manchester on 16 November after the boy overlaid the French flag on his profile image as a sign of respect to those who died when terrorists armed with Kalashnikov AK-47 rifles launched their attacks in the French capital on 13 November.
Some parents reportedly pulled their children out of school after seeing the photo.
The boy and his family were said to be "hugely upset" at the offence caused and deleted the photo but the image is still online on some Facebook pages showing the boy's face.
The school's headteacher quickly wrote to concerned parents telling them police had been contacted over the photo, which was first posted online in August. Greater Manchester Police have confirmed no criminal offence has taken place.
In the letter to parents, head Dr Kevin O'Hagan said he immediately contacted the boy's parents when the school was made aware of the image and the council and police were also called in.
Dr O'Hagan wrote: "The child and family were fully co-operative and are hugely upset that offence has been caused.
"They stressed their disgust at the Paris attacks, quickly deleted the Facebook account and wish to express their regret at what happened.
"I hope you are assured that the safety of all pupils and staff is our highest priority at this school and I want to take this opportunity to reassure all parents and carers that your children are completely safe here.
"The incident is a reminder of the need to use social media appropriately and safely at all times and we will, of course, continue to teach children about how to do this."
A spokeswoman for GMP said: "Greater Manchester Police has been made aware of an image on a social media site.
"The image has since been removed and police have spoken to the individuals concerned where it was deemed no offences have taken place."