Madison police say the person who killed UW-Madison student and Marshfield native Brittany Zimmermann broke through a door to get into her apartment.

They say that kind of information typically withheld from the public, but they opted to release it to warn neighborhood residents to take extra safety precautions.

Police are focusing their investigation on homeless and transient men.

Approximately two dozen of them have been arrested for other alleged crimes.

Officials have not released a cause of death for Zimmermann, 21, who was found dead in her apartment located about two blocks from the capitol April 2.