A good Samaritan neighbor raised the alarm after an elderly Lantau Island resident drank poison.
A police spokesperson said the 73-year-old man had drunk half a glass of herbicide after having an argument with his son.
His neighbor had gone to visit the man about 7am on Monday to find him unconscious. He called police and a helicopter took the man to Pamela Youde Nethersole Hospital.
Police have deemed the incident not suspicious.