Megan Somerville’s sister has made a statement about the alleged motorway stabbing

The sister of a woman accused of stabbing her own children on an Adelaide motorway has made an emotional statement as the family grapples with what happened.

The sister of a woman accused of stabbing her own children on the side of the road says her sibling has been battling mental health issues for years.

Megan Somerville, 35, of Modbury Heights, allegedly stopped her silver Honda sedan at the South Rd and Grand Junction Rd intersection of the North-South Motorway at around 11.30pm, on Monday, removed her children from the car, and stabbed them multiple times. In a social media post on Tuesday, Jessica Somerville said her sister, who has been charged with two counts of attempted murder, had multiple contact with both the Child Protection Department and SA Police.

“Despite repeated interactions with SAPOL and the Department of Child Protection, the system has failed to appropriately intervene,” Jessica said.

Megan Jayne Somerville, 35, of Modbury Heights. Picture: Facebook

Jessica said the children shouldn’t have been in her care and other alternatives considered.

She said the family was still trying to piece together what allegedly happened on Monday night but her sister had been battling mental health and drug addiction for the past eight years.

“We are still learning how things got to this point and need time to understand what happened that led to this,” Jessica said.

“Megan has had severe mental illness and drug addiction problems for the past eight years and despite the efforts of family and friends, she has continued to deteriorate with a number of incidents over the years.”

In 2018, SA Police reported Megan Somerville as missing while she was “heavily pregnant”, with concerns “held for her welfare as she suffers from a medical condition”.

At a press conference on Tuesday, police said a passing motorist stopped and intervened on Monday by disarming the woman, which likely saved the lives of the boys, aged three and eight.

Other people helped detain the woman until police arrived.

“We are extremely grateful to the people that stopped and rendered assistance,” Superintendent Selena Dinning said.

“No doubt, the situation would have been much different had they not stopped. We think he was very brave in doing this and we are really pleased that he was in the right place at the right time.”

Police at the scene at South road overpass, Wingfield, where a women stabbed two children overnight. Picture: 7NEWS

She said police had not established what led to the “frankly quite horrific” scene on the overpass. “We don’t know what triggered the episode, we don’t know at this point in time where she was going or what she was doing,” Supt Dinning said.

Yesterday, the little boys underwent surgery at the Women’s and Children’s Hospital to treat their wounds while their mother remained under police watch in hospital.

Police said both boys were in a stable condition on Tuesday night.

Alex Ellis arrived on the scene shortly after the horrific incident unfolded.

“There was a lot of blood,” Mr Ellis told 7 News.

“A couple of jumpers were used to help the wounds.”

Mr Ellis echoed Supt Dinning’s praise for the hero who came to the boys’ rescue.

“When I turned up there, there was an absolute champion who was helping, doing what he could to keep the situation under control,” he said.

“He deserves a medal, he’s brilliant.

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“I just know that there was a knife not far away and I know he had restrained her and he told us that he prevented this woman from doing more stabbing.”

“To keep the woman restrained was just an incredible thing to start with, but then … to ascertain what the problem was with the kids.”

Mr Ellis said the event was “pretty horrific” to witness.

“I’ve got kids myself … you don’t like to see that sort of thing,” he said.

7 News reported that witnesses heard Ms Somerville yell “Mummy loves you” as she was taken away from the scene.

A state government spokesperson said the family had been provided with support from a “range of organisations”.

“Our love and thoughts are with these two children,” a spokesperson said. “This matter is now under criminal investigation; as a result we are unable to go into specific details.

“Various supports from a range of organisations have been provided to this family given the complexity of their circumstances.

Supt Dinning did not confirm whether or not the family was known to police.

However a neighbour of Ms Somerville, who asked to remain anonymous, said police attended the home on Sunday.

Magistrate Luke Davis on Tuesday remanded Ms Somerville while an investigation was conducted into her mental competence. Omar Ali, duty solicitor for Ms Somerville flagged mental health as being a factor in the case.