A second person has been arrested by police investigating the murder of a pregnant woman in Donaghadee, County Down.

Sarah Montgomery, 27, was the mother of two young girls and expecting her third child when she was pronounced dead at her Elmfield Walk home on Saturday afternoon.

A 42-year-old woman was arrested in Belfast on Monday on suspicion of assisting an offender, while a 28-year-old man who was detained on suspicion of murder remains in police custody.

The police have said both suspects “were known to the victim and at present, no-one else is being sought in connection with the crime”.

The police were first alerted to an unconscious and seriously injured woman inside the Elmfield Walk house on Saturday afternoon. Ms Montgomery was then treated by emergency services but pronounced dead at the scene.

The Police Service of Northern Ireland (PSNI) described the case as “deeply tragic” and said it would “do everything in our power to bring anyone involved in this senseless murder to justice”.

On Monday, detectives issued a public appeal for information about a specific vehicle in east Belfast as part of their investigation.

They are seeking sightings of a yellow Jeep Avenger in the Airport Road area of the Belfast Harbour Estate on Friday afternoon.

“We are working at pace to determine the circumstances of Sarah’s tragic murder and need help from people in the Donaghadee and Belfast areas,” said Det Ch Insp Tom Phillips.

“This is an incredibly tragic case which has devastated Sarah’s family and friends, and leaves two small children without their beloved mum.”

He explained that officers want to hear from witnesses who may have seen anything suspicious in Elmfield Walk, Donaghadee, between 13:20 and 14:20 BST on Friday.

They are also appealing for sightings of the yellow Jeep between 15:30 and 16:15 later that same day.

“Do you have CCTV, dashcam or phone footage which could be useful in our investigation?” Det Ch Insp Phillips asked.

“Even if you think it may not be important, please come forward and speak with us as even very small pieces of information could prove invaluable to us.”

Ms Montgomery was the 27th woman to be murdered in Northern Ireland since the start of 2020.

Teddy bears, tributes and flowers have been left near the scene of her death at Elmfield Walk.

One of the tributes left outside her house described her as a “beautiful, kind and wonderful mother”.

Northern Ireland’s First Minister Michelle O’Neill said her death underlines the “epidemic in our society” of violence against women and girls.

Speaking in the Northern Ireland Assembly, she described the issue as a “scourge” and a “huge societal problem that we all share”.

“Another young mother, her life being taken,” O’Neill said as she expressed her sympathy with Ms Montgomery’s family.

“It’s just such a tragedy and it just really underlines for us all once again that we have a huge problem in our society with violence against women and girls.”

Women’s Aid NI released a statement on Monday, noting that of the 27 woman murdered in Northern Ireland since 2020 “the vast majority… were killed in their own homes”.

The organisation expressed its “sincerest condolences” to the victim’s family, friends and the wider Donaghadee community.

“Please know you are all in our thoughts at this incredibly difficult time, and we can’t even begin to understand your devastating loss,” it added.

by Kelly Bonner, BBC News NI reporter

At the home of Sarah Montgomery in Donaghadee, neighbours and friends have left flowers and blue teddies.

One note, paying tribute to a “beautiful, kind and wonderful mother” adds: “Thinking of you and your family and your 2 girls.”

Another note says: “So sorry, Sarah. You were a great mummy and a lovely girl.”

Near where these tributes have been laid, the police cordon at her house is still in place as officers continue to investigate.

Local residents who spoke to BBC News NI over the weekend described her as a bright, bubbly and loving mother.

The local MP, Alex Easton, said Ms Montgomery’s children attended the same primary school as his own grandchild and she was regularly seen on the school run.

“She’s been described as somebody who kept to herself and never was in any bother,” he told the BBC’s Good Morning Ulster programme.

He said he had been speaking to residents in Donaghadee over the weekend and they were still “extremely shocked by what’s happened”.

Easton described the murder as “wrong and barbaric” and said more action is needed to protect women and girls.

“I think Stormont maybe needs to look at doing some sort of education in our schools – that our children are taught that violence against women is totally wrong,” he added.

Alliance councillor Hannah Irwin revisited the scene on Monday and told Good Morning Ulster it was “particularly poignant” to stand next to the tributes.

She said two young girls had lost their mother and she could not imagine what the children must be going through.

“I know there’s just a palpable sense of shock in the Donaghadee community at the minute to see such a young life taken so soon,” she told the programme.

Irwin said Northern Ireland has “a serious problem with violence against women and girls and we need to be doing more about it”.

The councillor argued that education and early intervention was needed “so we can reach a stage where women aren’t losing their lives and women aren’t being abused or assaulted”.

“We need to tackle that pervasive misogyny in society first off, so we don’t reach that stage in the first place.”

Ulster Unionist councillor Mark Brooks said he knew Ms Mongomery and several of her family members and described her as “a lovely girl”.

“The community are shocked and stunned at brutality of the attack,” he said.

“I can’t imagine how Sarah’s little girls are feeling today,” the councillor added.

“Sarah won’t be forgotten.”

SDLP assembly member Cara Hunter said it was a “devastating tragedy”.

“A woman has lost her life in an act of violence, and children have lost their mother, with their world changed forever,” she said.

“There is no grief more profound than that of a child robbed of the love, safety, and care of their mother.”