The police in mainland China said today that they had arrested the suspected gunman in the slaying of a prominent Hong Kong businessman, a case that has fed fears of crime in Hong Kong as border controls are relaxed. Hong Kong finds itself in a race, as its police force tries to improve cooperation with mainland police forces faster than the number of criminals from the mainland increases here. Human rights concerns about close ties with the police across the border, where violations of civil liberties are common, have received little attention here because of the crime fears. The slain businessman, Henry Lam, was a stock market speculator, real estate developer and financial backer of mainland China’s biggest golf club. He had been eating breakfast at the Luk Yu Tea House, one of Hong Kong’s most famous restaurants serving dim sum. Full Story