A woman whose seven-year-old daughter was fatally shot in the head by her ex-partner told police weeks earlier that he might attack the family, the Guardian has learned.

Lyndsey Shipstone, 42, is understood to have told Sussex police she was concerned about a possible attack by her estranged ex-partner Yasser Alromisse, 46, who officers knew had a violent past.

On Thursday, Alromisse turned up at Shipstone's house in Northiam, East Sussex, and fatally shot their daughter, Mary, before killing himself inside a silver Toyota parked on the driveway.

The incident raises questions for Sussex police, whose officers had been in contact with Shipstone in the weeks and months leading up to the killing.

Shipstone was moved to a secret address in the quiet village of Northiam, near Rye, last year with Mary and her older son, Stephen, 21, to escape Alromisse.

The pair were involved in a bitter custody battle over the children and Alrimosse was believed to pose a threat to the family due to his history of domestic violence.

Since moving to Northiam, the family had been in contact with police and Shipstone is understood to have raised concerns with a local sergeant that her ex-partner was capable of attacking the family.

Egyptian-born Alromisse is thought to have discovered their address months ago through court papers. He was seen last week staking out the area in his Toyota Rav 4 vehicle.

Shipstone married Alromisse in Liverpool in 2005 after she converted to Islam, but the pair later separated. After the split, Shipstone lived with her children in Brighton between 2009 and 2011.

Investigators are waiting to take a full account from Shipstone. The case may face an investigation by the Independent Police Complaints Commission. The police watchdog had not received a referral from Sussex police by Monday afternoon.

The force declined to comment on any warnings it may have received about Alromisse. A spokesman said: "We're investigating the circumstances of how Alromisse came to be at the house in Northiam. At this stage, we are still trying to confirm how he discovered the address."

The area's police and crime commissioner, Katy Bourne, said: "The untimely and tragic death of Mary Shipstone has no doubt had a profound effect on her family, the local community and everyone who knew her. In my role as PCC, I will be closely following the progress of the police investigation and the circumstances around Mary's death."

Neighbours said Alromisse was waiting in his car for his daughter and ex-partner as they walked home from nearby Beckley Church of England primary school at 4pm on Thursday. Shipstone screamed: "He's got a gun" before Alromisse shot Mary twice in the head.

Armed police arrived at the scene within minutes and found Alromisse slumped inside his car with a self-inflicted bullet wound. Mary was flown to King's College hospital in London where she died of her injuries shortly before 3pm on Friday.

In a statement issued through Sussex police, Shipstone and her son Stephen said: "We are grieving the death of our beautiful and loving Mary."