Tiruvallur: A police head constable died and three others, who were part of the flying squad, were injured after the vehicle in which they were travelling met with an accident in Ponneri early on Wednesday. Police said that the flying squad was engaged in random vehicle checks on the area when the mishap took place. The victims were travelling in a Tata Sumo when another car coming in the opposite direction came too close to their vehicle. Their car swerved to the left to avoid the oncoming vehicle and rammed into a tree. Investigation is on.