The United States Bureau of Justice Statistics has spoken of "almost no time break between murders", but some academics consider that a killing spree may last weeks or months, e.g. the case of Andrew Cunanan, who murdered five people over three months.
[1] The U.S. Federal Bureau of Investigation (FBI) has found the category to be of no real value to law enforcement because quantifying a "cooling-off period" is arbitrary.
[2][3] The Encyclopedia of Crime and Punishment lists five different categories of spree killers and cites Mark O. Barton as an example of the second one.
[5] In The Anatomy of Motive, John E. Douglas cites Charles Starkweather and Andrew Cunanan (who murdered five people over three months) as examples of spree killers,[6] while Jack Levin calls Starkweather a mass murderer and Cunanan a serial killer.
In Sexual Homicide, Ressler, Burgess and Douglas gave more emphasis to killings being at more than one location, and less precision about the time span, saying that a single event can last a short or long time, citing Christopher Wilder's seven-week "murder event" or "killing spree".