Chief Dekmar, 61, a New Jersey native raised in Oregon, embraces a view of law enforcement that extends beyond the narrow goals of protecting the good and locking up the bad.

He tends to speak about his department as one organ of a broader social body, though one that is perhaps more exposed than others to its ills. He leads regular meetings of a “community outreach committee” in which he shares with other civic leaders what his officers see on the streets — homelessness, juvenile delinquency, children with learning and literacy issues — and looks for ways that various small-town entities might work together to solve them. He has also sought to address trust issues: The department, he said, has mandated the use of body cameras on officers for the last five years.

The chief became familiar with the lynching of Mr. Callaway only about two or three years ago, when one of his officers overheard two older African-American women who were looking at old photos of the LaGrange police on display at the headquarters building.

One woman said to the other, “They killed our people.”

Chief Dekmar began researching the episode but found, he said, only “sketchy reports” — there was “no investigation I could find, no arrest, no follow-up by the media.”

Indeed, the details of the crime appear to have been deliberately obscured for the 1940-era residents of LaGrange. Then, in 2014, Jason M. McGraw, a student at the Northeastern University School of Law in Boston, wrote a research paper about the lynching. He noted that while newspapers around the country had reported that a band of masked whites had abducted Mr. Callaway, the local paper, The LaGrange Daily News, wrote only that Mr. Callaway had died “as a result of bullets fired by an unknown person or group of individuals.”

The paper’s headline on the Sept. 9, 1940, article declared, “Negro Succumbs to Shot Wounds.”

Mr. Callaway is generally believed to have been 16 or 18 years old on Sept. 7, the day he was arrested and charged with trying to assault a white woman. According to Mr. McGraw’s research, six white men arrived at the jail that night with at least one gun, forced the jailer to open the cell and forced Mr. Callaway into a car. He was driven to a spot eight miles away and shot in the head and arms.