A 16-year-old boy died after apparently being hit on the head by a cricket ball while at school.
Kyle Rees suffered a serious head injury during the incident at Portchester School, in Bournemouth, Dorset.
Dorset Police said the incident happened on Monday at 2.10pm and Kyle was taken by ambulance to Bournemouth Hospital. He was later transferred to Southampton General Hospital where he died.
A 16-year-old boy was arrested in connection with the incident, initially for an offence of assault and subsequently on suspicion of manslaughter. He has been released on bail while inquiries continue.
The force said it had been informed of the incident at 7.30pm and officers are continuing to investigate. A police cordon remains in place at the school.
Teachers and children have been helping police with their inquiries throughout the day and the local Safeguarding Children's Board has been informed.
Debbie Godfrey-Phaure, executive head of Portchester School, said: "Students and staff are devastated by this terrible tragedy and our hearts and prayers are very much with the boy's family and friends.
"It is difficult to know what to do for the best in these distressing circumstances but our focus must be providing as much support as possible to our close-knit school community as we all try to come to terms with what has happened. The next few weeks and months are going to be emotionally testing for our students and staff, but we will be doing all we can for them.
"We are also fully assisting the authorities with their investigations. The emergency services cannot be praised highly enough for their prompt actions at the time, and we also pay tribute to the outstanding medical help he received at hospital.
Kim Drake, service director for children's social care at Bournemouth Borough Council, said: "We have set up a counselling service at the school to offer pupils, staff and parents support following this tragic incident at the school and we are currently working with both the school and the police with their investigation."