Brittany Zimmermann, the UW-Madison junior found killed in her apartment last month, called 911 before she died, Dane County officials confirmed Thursday.

Joseph Norwick, 911 Center Director, said Zimmermann made the call from her cell phone but was disconnected after a dispatcher did not hear anything and mistook Zimmermann’s call for an accidental or “hang up” call.

Madison Police Chief Noble Wray said police were not notified of Zimmermann’s 911 call, but should have been dispatched to the scene. Norwick said the MPD does not want any audio from Zimmermann’s call, content of the call, or time the call was placed released as to not compromise the ongoing homicide investigation.

According to Norwick, policy procedure instructs dispatchers to call back hang up calls to verify there is no emergency. After receiving Zimmermann’s call, Norwick said the dispatcher answered a second call, which was determined to be an actual hang up. The dispatcher then called the second number back, confirmed it was an accidental call and proceeded to answer a third 911 call regarding an unwanted person in a residence.

If a hang up call is made from a landline, the 911 Center automatically dispatches police to the residence, however, if a call is made from a cell phone, a call back to the number is the only method used to verify there is no emergency. Norwick said cell phone calls account for over 60 percent of calls the center receives.