A man in his 20s has died and a teenage boy is critically injured after a stabbing at a Northampton skate park. Northamptonshire police opened a murder investigation following reports of an altercation at the park in Ringway, Briar Hill on Wednesday. Despite help from bystanders and emergency teams, the man was pronounced dead at the scene. The teenage boy was rushed to hospital with life-threatening injuries where he remains in critical condition. Four people have been arrested and are in police custody. They include two teenage boys, a man, and a woman, all from Northampton. DCI Torie Harrison from the East Midlands special operations unit said, "This is a tragic incident in which a man has sadly lost his life, and a teenage boy is in a critical condition. Our thoughts are firmly with both their families at this difficult time." She added, "High-visibility police patrols will be taking place in the area to reassure the local community, and I would encourage anyone with concerns in the area to approach one of our officers who will be happy to help." Police cordons remain at the skate park and several nearby roads are affected. People are urged to avoid the area. Officers continue house-to-house inquiries alongside increased patrols to support the community. Authorities appeal to any witnesses or people with information who have not yet come forward to contact the police as inquiries progress quickly.