Detectives are continuing to appeal for witnesses to come forward, and Det Ch Supt Debbie White has called on anyone with information to contact the force “as a matter of urgency”.
Football club Guildford City, which has its home ground near the scene, said it was “devastated” at the news of the boy’s death.
In a statement on social media, it said: “All of our players, coaching staff, board members and volunteers send our thoughts and prayers.”
Meanwhile, Guildford Borough Council leader Julia McShane said she was “shocked and saddened” at what has happened.
“The loss of a young life in this way is utterly devastating and my heart goes out to their family and friends at this desperately sad time,” she added.