Authorities in Wisconsin say a likely cyberattack has affected the city of Madison's website and email system, as well as computers used by law enforcement countywide.

Dane County Emergency Management said the city began experiencing a high volume of Internet activity consistent with an outside attack late Monday.

The apparent attack comes three days after a Madison police officer on Friday shot and killed an unarmed 19-year-old. Similar attacks have occurred in other communities after officer-involved shootings, including in Ferguson, Missouri, after the death of Michael Brown.

Madison police told the Wisconsin State Journal that the department's officers experienced problems for about an hour. The newspaper reports the city's website was back online around 9:45 p.m. after several hours of down time.

It was not immediately clear who was responsible.