Former Dallas Police Chief David Brown, right speaks to reporters after Mayor Lori Lightfoot, left, nominated him to be Chicago's next police superintendent Thursday, April 2, 2020. (Tyler LaRiviere/Chicago Sun-Times via AP)

Former Dallas Police Chief David Brown, left, speaks to reporters after Mayor Lori Lightfoot, right, nominated him to be Chicago's next police superintendent Thursday, April 2, 2020. (Tyler LaRiviere/Chicago Sun-Times via AP)

Acting Superintendent of the Chicago Police Department Charlie Beck speaks to reporters about his support of Mayor Lori Lightfoot's decision to nominate former Dallas Police Chief David Brown as Chicago's next police superintendent, Thursday, April 2, 2020. (Tyler LaRiviere/Chicago Sun-Times via AP)

Acting Superintendent of the Chicago Police Department Charlie Beck, left, pats newly nominated Chicago Police Superintendent David Brown on the back, Thursday, April 2, 2020. (Tyler LaRiviere/Chicago Sun-Times via AP)

Former Dallas Police Chief David Brown, left, speaks to reporters after Mayor Lori Lightfoot, right, nominated him to be Chicago's next police superintendent Thursday, April 2, 2020. (Tyler LaRiviere/Chicago Sun-Times via AP)

Former Dallas Police Chief David Brown, speaks to reporters after Mayor Lori Lightfoot nominated him to be Chicago's next Police superintendent, Thursday, April 2, 2020. (Tyler LaRiviere/Chicago Sun-Times via AP)

FILE - In this June 15, 2015, file photo, Dallas Police Chief David Brown briefs the media about a shooting at Dallas Police headquarters in Dallas. Chicago Mayor Lori Lightfoot on Thursday, April 2, 2020, named Brown to lead the police force in the nation's third largest city. (AP Photo/Tony Gutierrez, File)