ANN ARBOR, MI - Investigators believe the person or persons who killed a retired University of Michigan professor in his home last week were injured in the incident.

Police investigating the death of retired chemistry professor Robert Sharp, 77, believe the killer may have suffered injuries to the face and hands, Ann Arbor Police Det. Sgt. Earle Fox said.

Sharp's body was found Monday morning, June 11 in the basement of his townhouse in the 3200 block of Alpine Drive. Police said they found evidence of foul play at the scene, but have not elaborated as to the apparent cause of Sharp's death.

Police were called to the home that evening to conduct a welfare check on Sharp after he failed to show up to a meeting at the condominium complex where he lived, neighbors said.

Investigators believe Sharp died sometime between the night of June 10 and the morning hours of June 11. Police have declined to release any details on how Sharp died.

The Ann Arbor Police Department is now offering a reward for information leading to the arrest and conviction of the person or persons responsible for Sharp's death.

Anyone with information about Sharp's death can call the Ann Arbor Police Department tip line at 734-794-6939, Detective William Stanford at 734-323-2628 or send an e-mail to tips@a2gov.org

Sharp began teaching chemistry at the University of Michigan in 1969 and served on the faculty for 39 years before his retirement in 2008.

His wife Maria Sharp recently died of cancer on April 20.