MADISON, Wis. —  A college student apparently called 911 from her cell phone shortly before she was killed but a dispatcher hung up, failed to call back and never sent police to investigate, authorities said Thursday.

Madison Police Chief Noble Wray said it was too early to know whether a better response could have prevented the April 2 slaying of Wisconsin-Madison student Brittany Zimmermann or helped police capture her killer.

Authorities refused to release the content of the phone call, but Wray said it should have been enough for the Dane County 911 Center to take it seriously.

"It would be accurate to state that there is evidence contained in the call, which should have resulted in a Madison police officer being dispatched," Wray said at a news conference. "The 911 center did not call back to the telephone number, Madison police were not notified and no officer was sent."

Zimmermann, 21, was found slain in her apartment in an apparently random crime. Police believe someone broke into her apartment before killing her. They have not identified a suspect but have ruled out her fiance, who found her body in the apartment they shared.

Dane County Public Safety Communications Director Joseph Norwick said the dispatcher who received the call from Zimmermann's cell phone inquired several times to determine whether an emergency existed. The dispatcher hung up after receiving no answer and then answered another 911 call that was waiting, he said.

The dispatcher failed to call the number back as required under the department's policy, Norwick said.

Norwick said he was investigating the incident and reviewing whether policies should be changed and employees should be disciplined. But he also said, "I don't think there's anything to apologize for at this time."