A detective who questioned a man accused of murdering four members of a Muslim family in Ontario is telling a jury the accused's demeanour changed, becoming more subdued, during his second police interview in the aftermath of the attack.

Nathaniel Veltman - who has pleaded not guilty - is charged with four counts of first-degree murder and one count of attempted murder for deliberately hitting five members of the Afzaal family with his truck while they were out for a walk in London, Ont.

Prosecutors have alleged Veltman's actions in June 2021 amount to an act of terrorism.

Detective Micah Bourdeau says Veltman's demeanour changed over time at the police station where he was held, with the accused becoming quieter and more subdued during his second interview - which took place about 13 hours after his arrest - compared to his first interview four hours after the attack, when Veltman was more talkative.

Bourdeau says Veltman declined during the second interview to answer questions about specifics or topics that appeared to be difficult for him to talk about.

The detective says he didn't have any concerns about Veltman's change in demeanour because it appeared to be normal, given the circumstances.

The trial has seen video of Veltman saying he was “shaken up” after the attack.

Jurors have also seen video of Veltman telling the detective he felt relieved after carrying out the attack, which he said was motivated by white nationalist beliefs.

Salman Afzaal, 46, his 44-year-old wife Madiha Salman, their 15-year-old daughter Yumna and her 74-year-old grandmother, Talat Afzaal, were killed in the attack. The couple's nine-year-old son was also seriously hurt but survived.

The trial, which is taking place in Windsor, Ont., is expected to last eight weeks.

This report by The Canadian Press was first published Sept. 19, 2023.