Stockton Police Chief Stanley McFadden has told people to "be alert" and have their heads "on a swivel" as they search for the gunman.

Police investigating five fatal shootings in California believe a serial killer might be on the loose in the state.

Detectives released a grainy image of a "person of interest" after the latest killing shortly before 2am on Tuesday.

The surveillance footage image shows an individual from behind who is dressed all in black, with a black hat.

Rewards totalling $85,000 (£76,000) are being offered for information leading to an arrest after the shootings.

Stockton Police Chief Stanley McFadden said the latest victim was a 54-year-old man, who was shot dead in a residential area.

8 July - an unidentified 35-year-old man described only as white was fatally shot at 12.31am

11 August - an unidentified 43-year-old man described as Hispanic was killed at 9.49pm

30 August - an unidentified 21-year-old man described as Hispanic was fatally shot at 6.41am

21 September - an unidentified 52-year-old man described as Hispanic was killed at 4.27am

27 September - an unidentified 54-year-old man described as Hispanic was fatally shot about 1.50am