A heavily-pregnant woman who fell to her death from a car park before her three young children were found dead had split up with their father the previous night, a neighbour said.
Fiona Anderson, who was named locally, suffered fatal head injuries at a multi-storey car park.
The 21-year-old mother's next door neighbour said Ms Anderson was worried that her children would be taken away from her.
"She was crying out for help because she was depressed, she couldn't cope", Megan Smith, 19, claimed.
"She had three kids, she was 21 years old, pregnant with her fourth - hormones take over, three kids under the age of three is a lot to take on at the age of 21", she added.
The children's father, Craig McLelland, sobbed as he visited the scene again today to leave flowers. He told reporters "get out of my face" as he and his mother left.
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Scotland Yard said the male youths will appear in custody at Westminster Magistrates' Court on Saturday.
Windy this weekend with gales across northwestern parts of the UK. Rain spreading southeast.
Greater Manchester Police said "inquiries are ongoing to fully understand the circumstances of the incident."