Chicago mayor and powerful political operative Rahm Emanuel appears increasingly entangled in his own cover-up of a white police officer's deadly shooting of 17-year-old African-American Laquan McDonald last year.

A new investigation by NBC5 reveals that Emanuel's top aides knew about the video depicting officer Jason Van Dyke's brutal shooting of McDonald well before the mayor claims to have been fully informed. The findings were based on internal emails obtained by the outlet through a Freedom of Information Act request.

The NBC5 investigation, available in the video below, provides further evidence of a cover-up.

Since officer Van Dyke killed McDonald with 16 shots while the teen was attempting to walk away on October 20, 2014, the city has vigorously opposed public release of footage showing the shooting. Van Dyke was not charged with murder until 13 months after the killing.

What's more, when city officials were forced earlier this month to release additional surveillance footage from a nearby Burger King, it showed an unexplained 80-minute gap covering the time the teenager was killed.

The missing footage aligns with the account of Jay Darshane, the manager of the Burger King that is located roughly 50 yards from the killing, who told a grand jury in November that police tampered with the restaurant's surveillance system, erasing roughly 86 minutes of footage.

The killing and cover-up sparked city and nationwide outrage, with the movement for black lives taking up the call "Justice for Laquan!"