Incidents of fatal police-on-police shootings are incredibly rare. But they do happen, and departments across the country have learned the hard lessons Baltimore is now facing after the killing of plainclothes Officer William H. Torbit Jr., The Sun reported this weekend.

A Harvard professor, who chaired a commission that looked into such incidents after two officers were killed in New York, said police will have to scrutinize not only the actions of the officers who fired on Torbit, but Torbit himself.

The incidents gathered by the commission show that criminal charges are rarely if ever brought. The panel found the "unconscious racial bias" plays a major role in off-duty or plainclothes officers being mistaken for suspects, and that departments often have gaps in protocols among their own officers and other agencies they may come into contact with. Black officers here and elsewhere say being mistaken for suspects comes with the territory, and at least one supervisor we spoke with said he was in favor of instituting uniforms for plainclothes officers so that they are more easily identified.

Click here to read the full report from the New York commission that looked into police-on-police shootings.