A GPS app alerted a woman that her ex-husband was skulking outside her house moments before he shot her dead, police say.

Catherine Taylor, 70, had been tracking her ex James using the Find My Phone app as she was fearful of his threatening behaviour, according to family.

She had recently moved in with her son in Fairfield, Connecticut, after attempts to rekindle her relationship with Taylor broke down.

The couple had divorced 25 years ago but had continued to live together for much of the intervening time.

But their recent relationship breakdown led to Taylor, 75, threatening that "things were going to get bad" for Catherine, her son told police.

Cpt Robert Kalamaras of Fairfield Police Department said: "It seemed like there was a build up in the relationship that it started to boil over."

On Sunday, she checked the app on her iPad to find that Taylor was stalking the grounds outside her home - moments before he allegedly broke in and killed her.

'CALL THE POLICE!'
Catherine is said to have screamed, "Call the police, call the police!" as Taylor smashed his way through glass and opened fire at around 9:30pm.

Catherine's son is then said to have wrestled with Taylor as he tried to reload his weapon, according to Fox61.

Taylor was left battered and bruised in the violent struggle before emergency services arrived.

Police said the suspect later appeared to be confused about why he was arrested, telling officers: "I can’t understand how I got here", the Connecticut Post reported.

A police report said: "When it came to providing specific details about what happened, (James) Taylor either did not recall or could not recall.

"He stated that he didn’t have a conceptual memory of what happened but he did remember being there.

"James Taylor stated that “I think trying to justify things like this is horrible".

It is reported that the couple had fallen out after Catherine accused Taylor of stealing vehicles from her and her 45-year-old son, who has not been named.

During this dispute, Catherine used the Find My Phone app to locate one of the cars - which police saw returned to her.

Taylor has been charged with murder, attempted murder, home invasion, first-degree burglary, third-degree assault and illegal discharge of a firearm.

He was arraigned on Monday on $2million bail as he awaits his next court date on February 19.