The 911 calls in the September 2015 death of off-duty Chicago police officer Donald Markham were released on Monday as authorities revealed they are investigating the case as a possible homicide.

The new probe comes after his wife, Dina, also a police officer, was found dead in the bathtub of the family home four months ago.

The medical examiner's office ruled she died of an accidental drowning after consuming a dangerous mix of alcohol and anti-anxiety drug Xanax.

At the time of her death, the FBI and Cook County prosecutors were investigating whether Donald's death may have been a murder and if the crime scene had been tampered with.

The Cook County medical examiner's office has not revealed why the tapes have been released, but the new investigation has been opened because of Dina's death and suspicions that police may have mishandled the original investigation.

Authorities said it was particularly concerning that no one tested Donald's wife for gunshot residue to rule out if she fired the gun.

The 911 calls in the September 2015 death of off-duty Chicago police officer Donald Markham (left) made by his wife, Dina (right), were released on Monday as authorities say they're now looking into the case as a possible homicide

In the tapes, Dina is heard telling an emergency dispatcher that Donald is unresponsive and bleeding from his head, and begs for an ambulance to come to their Norwood Park home (pictured)

On the tapes, Dina is heard telling an emergency dispatcher that Donald is unresponsive and bleeding from his head.

In her first call made at 3.06am, she yells: 'Please hurry! He's a PO (police officer)...There's blood all over the bed.'

Dina called 911 twice more, begging for an ambulance to come to the Norwood Park home, even as she's told help is on the way.

'Why can't you send one?...I need one now,' she pleads.

Donald's death was ruled a suicide via a self-gunshot wound to the head after a medical examiner conducted an autopsy.

Police reports from the time of the 51-year-old's death showed the narcotics officer had killed himself after drunkenly arguing with his wife at a bar and later at their home.

Dina had told police she was initially locked out of the house and found her husband dead in their bed when one of their children let her into the home.

Police reports indicate Dina then called 911.

Donald's death was ruled a suicide via a self-gunshot wound to the head after a medical examiner conducted an autopsy (Pictured, Dina and Donald Markham)

Dina (pictured), 47, was found dead in the bathtub of her Chicago home on May 28 in an apparent suicide

Then, on May 28 of this year, Dina was found dead in the bathtub, accidentally drowning after she consumed alcohol Xanax.

According to the Chicago Sun Times, a new probe into Donald's death had prior to the time of her death. A February 21 subpoena was sought about Donald's death from the medical examiner's office.

A Sun Times reporter had contacted Dina for comment about the new probe in the days before her death.

On May 22, she said she was 'unaware of the new investigation, would like to speak but needed a day to process it'. Then two days later when approached again, she told the publication she needed to 'protect herself and her children'.

The couple was married in 1995 and had five children together.

The medical examiner's office ruled that Dina (pictured) died of an accidental drowning after consuming a dangerous mix of alcohol and anti-anxiety drug Xanax

A day later she emailed the publication saying: 'In respect for the way you approached me, a friend of a friend will be in contact with you. I am unsure who that will be at this time, but he assured me he will follow through.

'My family and I have been through very difficult times, and it has been awful especially for my children. Should you proceed in writing a news story, I would appreciate a "heads-up" to prepare them.'

Investigators now want to know if Donald was killed, if police somehow mishandled the investigation or if officers were involved in a cover-up.

As well as removing Donald's body from the scene before it was examined by the medical examiner, there are concerns that no one tested his wife for gunshot residue to rule out whether she fired the gun.

Denis P Walsh, the lieutenant in charge of supervising the investigation into Donald's death, was accused three months later of mishandling a murder case he was looking after.

Steps were taken to fire him after Walsh admitted to keeping missing files at his home, but he resigned himself in February 2016.

For readers seeking help, please contact the National Suicide Prevention Line on 1-800-273-8255 or visit the website.