A guard attempted suicide hours after he injured three colleagues on an estate in Cheung Sha Wan yesterday morning. Police said the guard, 52, inflicted minor head injuries on his colleagues with a cutter and crowbar and left the Caldecott Road estate at about 12.30am. He called police at about 4am saying he was going to jump off a flyover. He was found under the flyover and taken to Princess Margaret Hospital in critical condition.