MADISON, Wis. (AP) -- The family of a murdered University of Wisconsin-Madison student is suing Dane County and the 911 operator who handled a call from the woman's cell phone.

Kevin and Jean Zimmermann are the parents of Brittany Zimmermann, a 21-year-old killed in her Madison apartment April 2.

The federal lawsuit dated Thursday alleges operator Rita Gahagan took Brittany Zimmermann's 911 call but lost contact with her, then failed to call back as required or send police to investigate.

The suit requests a jury trial and seeks unspecified damages.

A message left with Dane County Corporation Counsel Marcia MacKenzie was not immediately returned Friday. A telephone number for Gahagan was disconnected.