As spray painter Jason De Ieso worked away in his auto repair workshop, he was oblivious to a group of figures concealed in hoodies and masks striding purposely towards him across the shop’s sun-drenched car park.

The expectant father had never met the approaching men – some carrying sawn-off shotguns, another wielding a metal bar – but in a moment they would murder him in cold blood.

On Tuesday, after a mammoth five-month trial, a jury in South Australia’s Supreme Court found seven men guilty of De Ieso’s murder at his Pooraka business in northern Adelaide on November 21, 2012.

They are Musa Alzuain, 30, his brothers Husain Alzuain, 36, and Mohamed Alzuain, 32, as well as Daniel Mark Jalleh, 34, Ross William Montgomery, 38, Kyle Lloyd Pryde, 35, and Nicholas Sianis, 36.

But despite deliberating for more than 30 hours, the jury could not reach a verdict for Seywan Moradi, 36.

Declaring there was no prospect of coming to an agreement, Justice Brian Martin discharged the jury of their responsibility.

A ninth suspect has since died.

CCTV footage of the incident played during the trial showed four men at the head of the group approaching the shop’s roller door in an arrangement prosecutor Jim Pearce KC described as a “firing squad”.

Musa Alzuain, a former Olympic boxing hopeful, was fingered as the man responsible for pulling the trigger. He was 19 at the time.

De Ieso was described as an innocent man, senselessly slaughtered in the crossfire of a deadly gang war.

The nine men were associates of the Hells Angels motorcycle gang and had been embroiled in an escalating conflict with their rivals – the Finks.

The violence, which began in May 2011, included public brawls, drive-by shootings and a home invasion in which the young son of a bikie was shot in the leg.

It all culminated in the fire-bombing of the Alzuain brothers’ family home the day before the attack.

The men received a tip-off that their target, a Finks member, was at the Pooraka workshop, but they missed him by a matter of minutes and killed De Ieso instead.

Martin exempted the jury from all future jury service, given the extent of disruption the case brought to their lives.

“You did your job well and be satisfied in that knowledge that you’ve done the job well and served your community,” he said.

The seven guilty men were given a mandatory sentence of life imprisonment.

They will face court on December 11 for hearings regarding how long their non-parole periods will be.

Moradi will face court again on October 23.

– AAP