Florist Jennifer Milne, 28, told the High Court in Glasgow that she returned to the home she shared with Lee McCarthy, 31, and their three-year-old daughter to find the police there, four months after the blaze.
Despite having encouraged Mr McCarthy to go to the police, she told the court that she had a “wee mad moment” because he did not tell her what he was going to do.
“I was upset he hadn’t told me his intentions. I was crying and shouted at Lee. I was terrified for my daughter.”
The court has heard that this was the first of numerous statements Mr McCarthy gave to police about the fatal fire in Helensburgh, Argyll, and a number of other incidents.
Scott Snowden, 37, and Robert Jennings, 50, are on trial accused of murdering three members of a family by pouring petrol or something similar through their letterbox and setting fire to it.
Thomas Sharkey Jnr, 21, and his eight-year-old sister Bridget died in the blaze at their home in Helensburgh in the early hours of Sunday July 24 2011.
Their father, 55-year-old Thomas Sharkey Snr, died of his injuries in hospital six days later.
Between them Snowden and Jennings face 22 charges, all of which they deny.
Both men have lodged special defences of incrimination and alibi.
Snowden claims he was in Mexico when the fire at the Sharkey home was allegedly started and Jennings claims he was at home in Helensburgh.
FROM THE TRIAL SO FAR:
• Accused ‘sent Facebook message’ (17 May)
• Accused wanted to be ‘top man’ (15 May)