A group claiming to be part of ‘hacktivist’ organization Anonymous has taken responsibility for a cyber attack on the City of Madison.

The city was the target of a possible cyber attack Monday night and through Tuesday, according to a Dane County Department of Emergency Management statement.

According to the statement, Madison experienced a high-volume internet activity consistent with a cyber attack, known as “denial of service.” The statement said attacks like these have occurred in other communities following incidents similar to Friday night’s shooting on Williamson Street, in which 19-year-old Tony Robinson was killed and protests ensued.

Protesters gather after MPD officer shoots, kills 19-year-old black man

The attack affected internet based connections to city government. According to the statement, these connections include access to mobile data from public safety computers used by law enforcement, fire and medical emergency agencies throughout Dane County.

According to the statement, law enforcement officials believe the responsible individuals are seeking to “breach local government and public safety communications security systems.”

Public safety officials and local utility services have also been notified of the attack and its potential impact.

According to the statement, officials from Information Management and Emergency Management are monitoring the situation and the Dane County Emergency Operations Center has opened as a result of the attack.

At a press conference Tuesday afternoon, Madison Mayor Paul Soglin confirmed the cyber attack and said he was not surprised by it.

“I have every confidence that law enforcement will be able to handle it,” he said.

Soglin noted the city has frozen some online payment accounts, including those dealing with water bills and dog licenses.

He said he would not speculate who is behind the attack.

The “Anonymous” video sends an ultimatum to MPD and ends by saying, “you should have expected us.”

In response to the video Soglin said the city is always concerned, however it is prepared when threats like these occur. He noted the city’s internal communications systems are operating as usual.