CHICAGO (CBS) — Controversy is brewing inside the Chicago Fire Department about a tragic incident that happened on Labor Day weekend.

It began with a firefighter leaving work to check on his family. It ended with his wife’s death.

READ MORE: Chicago Police Officers Refusing To Report Vaccine Status Expected To Protest Outside Police Headquarters Tuesday

Now, as CBS 2 Political Investigator Dana Kozlov reported Monday night, several high-ranking department sources have come forward with concerns about how the sensitive matter was handled internally.

On Sunday, Sept. 6, during Labor Day weekend, Mary Jo Tsolokas was at her home in the Mount Greenwood neighborhood with her two young children and a friend.

Her husband, Chicago firefighter/paramedic Angelo Tsokolas, was on duty. But later that night, according to a police report, firefighter Tsokolas said his 7-year-old daughter called – concerned that Mary Jo Tsokolas was intoxicated.

Firefighter Tsokolas left the firehouse, went home, and put the kids in the car to take them to his mother’s. That was when Mary Jo Tsokolas ran to the sport-utility vehicle and firefighter Tsokolas hit and killed her – in what police later ruled an accident.

“Point blank – if he was mandated to stay at work, Mary Jo would have not been dead on Sunday night,” said a high-ranking Fire Department official who did not wish to be identified for fear of retaliation.

The official said indeed firefighter Tsokolas should have been mandated to stay at work. And the official is just one of several Fire Department sources who have reached out to CBS 2 with concerns about Mary Jo’s death – and questions about changes to firefighter Tsokolas’ time card after her death.

We’re told those concerns are now reverberating through City Hall.

“The dots do not connect correctly,” the official said.

The official said once on duty, firefighters are not allowed to leave their shift. An internal CFD memo from April expressly states that “companies are prohibited from leaving the firehouse unless dispatched by the OEMC for an emergency or other calls.”

Firefighters can trade shifts, but only 12 to 24 hours prior to the shift’s start.

CFD spokesman Larry Langford explicitly told CBS 2 that firefighter Tsokolas was off duty when he went home. Yet the police report from the incident stated Tsokoloas told officers he was on duty at the time.

READ MORE: Mobile City Hall Bringing City Services To Little Village Tuesday

“So he’s on duty, something escalates, and now all of a sudden, we have to cover up the fact that we have allowed him to leave the firehouse – which is a brink, or breach, of protocol,” the official said.

One source was so concerned that they gave us a screen grab of CFD’s internal scheduling system, which tracks shifts and hours.

That source said six hours after Mary Jo died, someone went into the system and changed it to show an emergency had been made prior to Mary Jo’s death.

Tsokolas is marked as having traded his shift at 10:30 p.m. the night he hit and killed his wife. But our source said a red circle with an X and a black one with a question mark next to Tsokolas’ name, and the name of his replacement, raise red flags.

Tsokolas Schedule

(Supplied to CBS 2)

“That simply means that whoever has the authority to manipulate telestaff did an illegal move. That’s what that means,” the official said. “Not allowed. And only a high-ranking individual with clearance to manipulate telestaff after hours could have done that.”

One source also said the small marking next to Tsokolas’ replacement’s name raises another concern.

“The question mark is indicative that the person has not been checked in,” the official said.

All of our multiple sources are concerned about why all of this was done in reaction to a tragic accident.

After repeated emails, the Fire Department spokesman insisted everything was above board. He said Tsokolas followed proper protocol and his supervisor ensured a replacement was found so he could go off duty immediately.

A representative of Mary Jo’s family said they still have many questions about her death and the circumstances surrounding it. But they are still grieving and did not want to comment for this story.

A Chicago Police Department representative told CBS 2 the investigation into Mary Jo Tsokolas’ death has been closed.

MORE NEWS: Police Release Video Of Suspects Wanted In Death Of 18-Year-Old Azul De La Garza