WILLIAMSON COUNTY, Tenn. (WKRN) — It only takes a couple of seconds for everything to change.

“I’m holding his hand and I pull him in and as I’m saying, ‘Babe, a car is coming,’ I just hear a thunk,” Heather Mix said.

The accident happened off Old Hillsboro Road in Leipers Fork where Mix watched her boyfriend Peter Mulcahy get hit by the car.

“As this is all happening, in my head all I can think about is how am I suppose to live a life without my best friend,” she said.

The two have been together for three years, making plans to go to Europe and even get married, but Mix almost lost Mulcahy after the two were walking to their shuttle with a group of people after a fundraiser event held in town Saturday Oct. 15.

“The most hurtful part is absolutely the fact now that they left him there whenever he just…he didn’t deserve that,” she said.

The Tennessee Highway Patrol released surveillance footage of the red Mercedes SUV they believe hit Mulchay and kept going.

“The fact that somebody would hit him and leave him in the road to die, and not even stop to help or to check just infuriates me,” said Mix.

Thankfully Mulchay will recover, and while Mix is grateful to everyone that helped him that night, she’s still hopeful they’ll find the person responsible for all of this.

“When you see the headline ‘pedestrian verses vehicle’, he’s not just a pedestrian, he’s a human who deserved the decency to make sure he’s okay and gets the help that he needed,” she said. “Even if it was an accident, there’s just no excuses to leave someone.”

THP is looking for a red Mercedes SUV that’s possibly a 2016 to 2020 GLA model with damage to the front end area, and a missing front Mercedes emblem.

If you witnessed the crash or have any information about the whereabouts of the driver or the vehicle, you are asked to call the THP Emergency Dispatch Communications Center at 615-744-3091, ext. 1, and speak with Trooper Healey.