The victim says on July 18 she was threatened with her life, tied with rope, gagged with duct tape and raped at a dirt path along a drainage ditch just west of Selma. Police said the victim did not know Muller.
According to a search warrant, police found pieces of rope tied to trees as well as duct tape, women's panties, a cigarette butt and a shovel were found at the scene.
It also revealed that an UPC code on the shovel was traced back to a Smithfield Wal-Mart, where investigators say Muller purchased the items just a few hours before the crime.
Authorities say store surveillance cameras showed a man that looked like Muller in a Jeep outside of the store. Inside, it showed the same man using Muller's credit card to buy a shovel, duct tape, rope, cable ties, a knife, condoms and a black shirt long sleeve shirt --the same kind of shirt the victim says her attacker was wearing.
During their investigation they discovered that Muller had kidnapped and tried to rape another woman in Smithfield back in May.
On Wednesday, he faced a judge for the first time on those charges. Despite the evidence, Muller's sister says she is standing behind her brother.
"I'm here to support my brother," Heidi Muller said. "I love him very much and I'm sorry for all the parties involved. And we don't know until we go to court what exactly has taken place."
Muller is currently in the Johnston County Jail under a $350,000 secured bond.
Heidi Muller says her brother was a Marine who fought in Iraq. He had recently been a paid firefighter with the City of Raleigh since May 26.
According to the Raleigh Fire Department, Muller was a new recruit still enrolled in its cadet training program when he was arrested.
RFD rules require a cadet to be on time. Because Muller is in jail and was a no-show Monday and Tuesday, the Chief says he's no longer a member of Raleigh's fire department, according to its attendance rules.
Police are still investigating if there may be more unreported incidents involving Muller in the Smithfield-Selma area, and encourage anyone with information to come forward.