A 15-year-old boy has been stabbed to death in a fight between two groups of young people in a park in Birmingham, police said.
Four teenagers were arrested following the attack at 17:55 BST on Monday in Wash Lane, South Yardley.
Hassan Mahmood was taken to hospital but died a short time later.
Two 16-year-old boys from the city remain in custody after being arrested on suspicion of murder. Two boys aged 15 and 17 were released without charge.
A post-mortem examination is due to take place on Wednesday and specialist liaison officers are supporting Hassan Mahmood's family.
'Gone too far'
Officers cordoned off the area and a floodlit search was carried out.
BBC WM reporter Michelle Dawes said several bouquets of flowers had been left outside Oaklands Park.
She said the brother and sister of Hassan were among those who laid flowers and tied balloons to the park's gates.
His sister said: "All I want is for everyone to pray for us as we come to terms with this great loss."
Det Insp Tom Chisholm said: "This was a tragic incident and our deepest condolences go out to the young man's family."
Police said they were looking at CCTV footage which may have captured the incident and were appealing for anyone who was in the area at the time to contact them.
Mr Chisholm said: "We are aware that there were groups of young people in the area, some of whom may have left the scene before the police arrived.
"There is some suggestion that this was a fight which has tragically gone too far."
The 15-year-old was a pupil at the Rightrack independent school in Saltley and his head teacher Sohail Aslam said the teenager had only recently joined them.
Mr Aslam said: "He had been with us six weeks but had settled very quickly and was well-liked by all the staff and students.
"He was very respectful towards everybody, we'd had no problems and he had a bright future."
The head teacher said Hassan had been studying for his GCSEs and enjoyed "sports and singing".
The school is considering some form of tribute to the pupil in conjunction with the boy's family.