During an operation in Tai Po Road, a driver accelerates his vehicle directly towards an officer who was trying to stop him Hospitals are on the alert for patients with bullet wounds after a police officer shot at a car that drove directly at him in Tai Po yesterday. Despite firing at point-blank range, Station Sergeant Chan Kan-wing of the New Territories North traffic unit may have missed the vehicle because he was lurching away as he opened fire. The incident happened while police were trying to stop cars racing illegally on Tai Po Road about 3.30am. Sergeant Chan was in an unmarked police car following about 20 racers as they headed towards a police roadblock. Two kilometres from the roadblock, the racers somehow became aware of it, and about 10 made U-turns near the Chinese University. The police car stopped and Sergeant Chan got out to halt the racers. The driver of a red Honda Civic accelerated towards him, and the officer fired a single shot as it went past, according to police investigators. A police source said: 'The car first stopped about five metres away from the station sergeant. When the officer approached the vehicle, it moved at high speed towards him.' 'The officer had no chance to issue a warning as he was in a life- threatening situation. He had to step back to avoid the car, drew out his service revolver and fired a shot as the car drove past, about a foot away,' he said. Officers said it was not clear whether the car was hit or its two occupants injured. It sped away with about seven other cars. Two cars stopped at the scene of the shooting and seven were intercepted at the roadblock. Three other cars were intercepted later. Twenty-one people - 13 men and eight women - were arrested. Yesterday's incident is the second time a policeman has opened fire in five months. A plainclothes detective fired three shots in an attempt to stop three knife-wielding men from hacking a mini-bus driver to death in Shau Kei Wan in April. His shot missed, and the three killers managed to escape. The shooting yesterday occurred after officers from the New Territories North traffic unit received a tip about the road racers. They set up their roadblock in the New Territories-bound lane of Tai Po Road near Savanna Garden Police said no officers were injured in the incident. After the shooting, officers cordoned off a section of Tai Po Road and mounted a search for the Honda until 7am. The 21 people arrested were released on $5,000 bail each, and have to report to police next month.