York Regional Police are asking for the public’s help in connection with the investigation into a serious crash on Friday.Police responded to a collision involving a Mercedes and a Subaru in the area of Major Mackenzie Drive and Stonebridge Drive near McCowan Road around 4:50 p.m.Investigators say one vehicle crossed over the centre median and struck the other head-on.Related:4 people injured, 2 critically, in Markham crashThe driver of the Subaru was taken to the hospital with life-threatening injuries. Two children in the vehicle were also hurt – one had life-threatening injuries, and the other had minor injuries.The driver of the Mercedes was also taken to the hospital in serious but non-life-threatening condition.As the investigation continues, police are looking to speak to witnesses who have not already come forward and to anyone who might have dashcam footage from the area around the time of the collision.Video can be uploaded to the YRP’s online portal here.