Friends and co-workers of Dylan Thomson have expressed their shock over revelations he was likely behind the house fire that killed him and his parents, Graeme and Ros, in Brisbane's north on Tuesday morning.

“I spoke to him numerous times on Friday and everything was good," the 24-year-old mechanic's employer Nick Ramsay told 9NEWS.

The young man has been described as capable and hard-working.

"He was just a kid that came to work and went home... to go from that and having a joke with him on Friday to now, it's just unbelievable," Mr Ramsay said.

Police are now investigating the Everton Hills blaze as a possible double-murder suicide, with Thomson the prime suspect.

The three family members' bodies were found in the charred remains of the house after fire destroyed the property.

Ros and Graeme Thomson (left and right) and their son Dylan (middle). (Facebook) (Facebook)

It is understood a domestic dispute between the trio sparked the blaze that claimed their lives.

The parents had recently separated, with Graeme flying back to Brisbane in the past few days to help his ex-wife deal with their son's increasingly volatile behaviour.

9NEWS can also reveal Graeme suffered a serious head injury before the fire erupted.

Graeme was an SES volunteer and helped save lives during Cyclone Debbie in 2017.

SES Whitsundays paid tribute to the former volunteer in a statement, saying "we have lost a great mate".

The fire caused massive plumes of smoke to reach into the sky. (9NEWS) (Nine)

"So hard to believe that his smile, mad humour and endless positive energy is no longer with us. He turned the Airlie Beach Group into an active, fully functional team that felt very much like a family.”

Police yesterday spoke to Dylan's workmates at Woodridge who told officers he was battling a drug addiction, the Courier Mail reported.

One employee at the engineering specialty store told the newspaper Dylan was trying to turn his life around and had even gained a promotion.

Graeme and Ros split in 2009, with Ros moving to Brisbane with Dylan after the break-up.

The fire and explosions caused significant damage to the property. (9NEWS) (Nine)

Graeme's brother Mark Thomson had been staying at the home being rented by Dylan and Ros to ensure the son was attending court.

“Graeme was there to make sure Dylan wasn’t going to do a runner, as he was to face court on a charge of abusing police,” he told the Courier Mail. “Graeme was a good man and would do anything for his kids.”

The uncle reminded people that the family had another daughter who lost her family in one morning.

SES crews were deployed to Everton Hills yesterday to search for a possible accelerant used in the blaze.

Fire crews were called to the property in Pavonia Street at 5.30am on Tuesday after reports of an explosion and the fire which sent flames up to four storeys in the air.

"It was a man who shouted help, that's all I heard, and then I saw the flames and pretty scary stuff actually, I thought we were all going to be for it," neighbour Chris Paul said.

"You could just see the fence and beyond the fence a blazing fire, and it was getting really high."

Queensland Fire and Emergency Services Superintendent Bevan Moore said: "Calls from neighbours have indicated there were unusual noises associated with the fire.

"There were explosions reported by neighbours, the smell of fuel, things like that."