Jailed gangland killer Carl Williams is mourning the death of his mother Barbara, who is believed to have taken her own life by overdosing on drugs.

The body of Barbara Williams was found in the bedroom of her home in Melbourne’s north-western suburbs on Saturday morning.

Police confirmed an empty pill bottle was found nearby in the bedroom where the body was found, adding her death was not being treated as suspicious.

She was said to have been suffering from depression after her son Carl was last year jailed for 35 years for the murders of three gangland rivals, while her estranged husband George Williams, 61, is also serving time for drugs convictions.

“We’ve been able to establish that she’s been suffering from severe depression for the last 12 months, there is an empty bottle of tablets beside the bed,” Victoria Police Detective Senior Sergeant Ron Iddles said.

“Here’s a mother whose brought up her children the best that she can and unfortunately Carl’s in jail and her husband’s in jail and that’s obviously had a massive effect on her.”

Police played down reports that gunshots had been heard in the hours leading up to the death, a spokeswoman saying there was no investigation into any gunshots.

It’s believed relatives and a local shopkeeper found Williams’ body after eventually forcing their way into the house in Primrose Street, Essendon, where she lived alone under tight security.

Police said they had established the deceased had last spoken to someone around 8pm (AEDT) on Friday.

Her ex-daughter-in-law, Carl’s ex-wife Roberta Williams, was pictured in tears in a car outside the house on Saturday.

Carl Williams was sentenced in May 2007 to a minimum of 35 years’ jail for the murders of three Melbourne underworld rivals — father and son Lewis and Jason Moran and drug dealer Mark Mallia.

His father, and his mother’s estranged husband, George was last year sentenced to four-and-a-half years’ jail after pleading guilty to trafficking a commercial quantity of methylamphetamine.

Author Adam Shand, who has written about Melbourne’s gangland war, said Carl was very close to his mother, though she had had a strained relationship with his ex-wife Roberta.

“He would spend as much time with his mother at home as with his wife Roberta, even the good days,” Shand told Sky News.

“He loved his mum’s cooking, he would go home regularly. Even during the height of the gangland war, police would often find him at his mum’s house.

“I think his sentence for 35 years hit his mother very, very hard. They were very close. He’s lost the real rock in his life, you could say.

“She [Barbara Williams] has been depressed for some time. Her life has been on a downhill slope.”

Corrections Victoria, which manages the high security Barwon Prison where Carl is being held, said the convicted murderer and his dad George — who’s serving time at Dhurringile prison in northern Victoria – were both informed of the death.

“Both Carl Williams and George have been advised. They have been allowed to speak to one another and we will provide appropriate support if required,” a Corrections Victoria spokeswoman said.

An autopsy would be carried out on Sunday, police said.