Police have linked several shootings to a possible serial killer in Stockton, Calif.

Stockton Police Department officials released this undated surveillance image of a person of interest. The figure appears to match the description of the only surviving victim of a suspected serial killer who has fatally shot six people. (AP)

Stockton Police have now linked seven shootings — six fatal — to a possible California serial killer who remains at large.

Officials confirmed that the string of seemingly random homicides began in April of last year — more than a year earlier than previously believed — and they warned there could be additional victims.