FBI agents have arrested a black student who allegedly threatened to shoot 16 whites - one for each bullet that hit a teen in a notorious police shooting.
Police officer Jason Van Dyke, who was charged last week with the murder of 17-year-old Laquan McDonald, was released on US$1.5 million bail, local media reported.
Van Dyke's release came just hours after the online mass shooting threat, allegedly by Jabari Dean, 21, caused the University of Chicago to close its doors.
A fellow user of the unidentified social media forum where the message was posted took a screen shot of the threat and showed it to the FBI on Sunday (local time).
The posting described a plan to bring an assault rifle and two handguns to the campus quad on Monday and to "execute" 16 white male students or staff members.
This was allegedly to be carried out to avenge McDonald, a 17-year-old black Chicago youth who was cut down in a hail of 16 police bullets in October 2014.
"I will then die killing any number of white policemen that I can in the process. This is not a joke," the message read.
"I am to do my part to rid the world of the white devils. I expect you to do the same."
Tensions flared last week after officials released a dashcam video showing police officer Van Dyke shoot McDonald after the teenager walked away from him.
The graphic video was the latest in a string of police shootings caught on camera that have sparked mass - and sometimes violent - protests.
The footage has fuelled an already acrimonious national debate about racism and the use of deadly force by police.
The University of Chicago, which had urged students and non-essential staff to stay away or remain indoors if already on campus, welcomed the arrest and said normal operations would resume on Tuesday.
Dean faces up to five years in prison if convicted of transmitting a threat.
Another college, The University of Illinois Chicago, had earlier identified the suspect as one of its students.