A 42-year-old man and a 48-year-old man died at the scene.
Tims, Thon and co-accused Semaj Cigobia, 18, were charged on July 16 over the double fatal arson.
Cigobia, who is on bail, on faced court where he was accused of assisting the two others in avoiding police detection by burning the car alleged to have been used in the offending.
Detective Senior Constable Elise Jinks on Thursday said Tims drove to the factory, jumped over a fence with a red jerry can full of petrol and allegedly set it alight.
She alleged Thon, who was in the passenger seat, handed Tims the jerry can, and said there was only one entry and exit point from the factory where the two victims were sleeping.
The pair were going to be paid A$4000 ($4400) by a prisoner to carry out the arson, she said.
“They were tasked by someone who is in prison and we haven’t been able to identify who that is,” she said.
Jinks said the price was “relatively low considering two people lost their lives”.
Tims was recorded on a surveillance device inside his car saying “it wasn’t supposed to happen, it was just a mistake, wrong place wrong time”, to his girlfriend in mid-July, she told the court.
“I did everything, I drove, I lit it up, I stopped, I got out, I jumped a fence,” she said Tims was recorded saying.
“It’s for a job ... for a buddy.”
Jinks said she had spoken to the family of the two victims ahead of the bail applications.
“The family would be incredibly disappointed if both Tims and Thon were released back into the community, given they’re still grieving the loss of their family members,” she said.
Thon’s sister said he was a “quiet kid” who stayed in his room at home most of the time.
“Our main focus is that he finds the right thing he wants to do with his life,” she told the court.
She said he would live with her and the rest of their family if released on bail, and she would report him to police if he breached his conditions.
“He should do the right thing, he’s not just out there to enjoy and have fun, he needs to follow the law,” the sister said.
A youth justice worker said, while Thon was eligible for supervised bail, she had assessed him as unsuitable due to the serious nature of offending and negative peer associations.
The hearing continues.