A former Marine is suing a Harley-Davidson dealership in Orange County, Calif., for allegedly taking advantage of his post-traumatic stress disorder to sell him an expensive bike.

Brett Smith, 25, filed a lawsuit against the Irvine dealership over a sale in early April. Smith's family tried to return the $17,000 bike two days after he bought it because he said he had made the purchase after five days of insomnia and wasn't thinking straight, according to court papers.

Smith was a member of the Special Forces deployed in Afghanistan and was discharged in 2010 after which he was diagnosed with PTSD and traumatic brain injury, said his attorney, Daniel Gilleon.

The sale in April happened after Smith had suffered from five sleepless nights due to his disorder, Gilleon told ABC News today.

"That day is very much a dream-like recollection to him," said Gilleon. "He wasn't completely aware of what he was doing."

Smith, who is unemployed, entered the Harley-Davidson dealership on a whim to buy a motorcycle, according to the lawsuit filed on Oct. 30. While there, he told the employees that he had PTSD, while pacing, sweating profusely and acting jittery.

"At one point, the salesperson even gave him water so that he could take his Xanax," said Gilleon. "He took three while he was there."

Smith told the salespeople that he would be driving straight from the dealership to Georgia, despite the fact that he did not have a motorcycle license, according to the lawsuit.

He left the dealership with a Harley.

After driving home on his new motorcycle, Smith decided to go to Georgia the next day, again without sleeping, court papers show. He packed a backpack full of fruit, clothes and a PlayStation, driving 40 miles before he realized he had no money and returned home, the lawsuit states. He checked into a hospital that night.

Smith decided to sue the dealership for unfair business practices after it refused to take the Harley back, even when Smith's family tried to explain his mental state, his attorney said.

"They just blew it off," said Gilleon. "Harley-Davidson touts itself as an all-American, patriotic company, but patriotic is as patriotic does. They exploited his mental condition because they were trying to make a sale. They got one, but they also got a lawsuit in addition to that."

The Harley-Davidson dealership declined to comment on the case when reached by ABC News.

Brett Smith claims a Harley-Davidson salesperson took advantage of his PTSD and sold him a $17,000 bike.