A man and two women suffered gunshot wounds after attackers opened fire on people attending a party in Harlow, Essex, early on Saturday.
Essex police said the man, who is in his 50s and from nearby Grays, was taken to hospital with life-threatening injuries.
Two women in their 20s were also taken to hospital with single gunshot wounds, which are not considered to be life-threatening.
Police were called shortly before 5am following reports that a number of people had arrived in a car and fired at a group who were at a party at the property in Roydon, Harlow.
Anyone with information is asked to contact the major crime team at Essex police or Crimestoppers anonymously on 101.