CHICAGO (CBS) — A brochure intended to serve as educational materials by the North Chicago Police Department for citizen training has racheted up racial tension in the far north suburb.

WBBM Newsradio’s Regine Schlesinger reports the presentation contained pictures many considered to be offensive to African Americans, including images of comedian Dave Chappelle’s crack addict caricature, Tyrone Biggums, and a black man in an orange prison jumpsuit, flanked by white guards.

At a city council meeting Monday night, Police Chief James Jackson admitted the document was crude and unprofessional.

“It displayed a lack of good judgment by the participating officers,” he said.

In an exchange with aldermen, Jackson said the brochure was the work of some of his officers, and was not meant to be offensive.

“They made a mistake,” he said. “They’re human, they made a mistake.”

Jackson said it was a misguided attempt at humor, and was not authorized by him.

The department was already embattled over allegations of brutality and corruption. Critics said the brochure is just another black eye for North Chicago police.

Jackson said an investigation has been launched, but that wasn’t enough of an explanation for some aldermen, who wanted to know if the officer responsible has been disciplined.