By Brad Edwards

UPDATED: 10:03 p.m. 4/20/16

CHICAGO (CBS) –One of Chicago’s top firefighters has resigned after a crash that sources say may have involved alcohol.

CBS 2’s Brad Edwards reports Deputy Fire Commissioner John McNicholas may have been drinking before he crashed his government-issued SUV early Wednesday morning, yet no tickets were issued.

McNicholas was in charge of operations, the third highest in command. He also handled discipline CBS 2 has been told.

Sources say he was on Lake Shore Drive and hit a pole tree and say any employee in such an accident in a city vehicle should be tested immediately.

CBS 2 has been told there were special exemptions given and there was a delay of several hours and he still tested over the legal limit.

CFD Capt. Carmelita Wiley-Earls told Edwards, “Here we go once again, a professional courtesy given to a brother firefighter…If anyone was driving drunk then they would have been arrested.”

Wiley-Earls said McNicholas “without question” should be fired.

Wednesday evening, Fire Department spokesman Larry Langford said in a statement, “Chicago Fire Department Deputy Commissioner John McNicholas was involved in a traffic accident in the early hours of April 20, 2016 near Lakeshore Drive and North Avenue in a department vehicle. The Deputy Commissioner has been fully cooperative with the Internal Affairs Division of the department. The investigation has thus far found that McNicholas was operating his city vehicle outside of department policy. Late this afternoon McNicholas tendered a letter to Fire Commissioner Santiago resigning his position as Deputy Fire Commissioner for Operations effective today. The investigation is ongoing.”

It is not clear if he only resigned his position as deputy fire commissioner or if he resigned from the department.

The Chicago Police Department says it is conducting a joint investigation with the Chicago Fire Department into the specifics of the accident.