CHICAGO (CBS) — The video showing the fatal shooting of Laquan McDonald by a Chicago Police officer touched off the firestorm of rage, protests, and even the firing of Chicago Police Superintendent Garry McCarthy.

Now, with the first-ever federal probe into the Chicago Police Department, many wonder what all of this, and the corrections, will cost, reports CBS 2’s Jeremy Ross.

Ferguson, Missouri and Chicago are very different communities and cases. Ferguson’s police department consists of about 50 officers, as compared with CPS’s 12,000.

One thing they have in common, a federal probe and perhaps a costly outcome.

U.S. Attorney Zachary Fardon didn’t answer reporter questions as he left Chicago Police Headquarters. The visit follows the 2014 killing of 17-year-old Laquan McDonald, shot 16 times by Officer Jason Van Dyke.

During a news conference, Mayor Rahm Emanuel acknowledged the short-term pain for the potential long-term reform gains.

“It’ll be a long bumpy road and this is just the beginning,” Emanuel said.

But as investigators go through documents, procedures and interviews the mayor hinted at how far back the probe could span.

“This is decades in the making,” Emanuel said.

The 2014 police shooting of 18-year-old Michael Brown led to unrest in Ferguson, Missouri and a federal investigation of that department in August.

The results were released about eight months later and about 16 months in, the city has yet to fully agree with the federal government on how it will implement reforms.

That could include new police training, improved record-keeping, and a person to watch over the transition.

The cost is estimated between $500,000 to $750,000. That could result in personnel cuts there, tax increases or both.

As for Chicago, who the Better Government Association says has paid out an estimated half a billion dollars in police-related settlements over the past decade, the possible additional cost to taxpayers remains unknown.

“We’re going to let officers know that we appreciate their work, but there’ll be no quarter left if they don’t do it in the most professional sense,” Emanuel said.

So when can we expect the results of this federal investigation? No word from the Department of Justice. The Ferguson investigation took months and it’s possible Chicago could take months or years.