Twenty-two-year old Gabby Petito and her boyfriend Brian Laundrie went on a cross-country trip this summer, but Petito never returned home. Her body was found near Wyoming's Grand Trenton National Park last month.Laundrie, who has been declared a person of interest in the case, disappeared a few days after Petito was reported missing. Several law enforcement agencies, body hunters, and volunteers are still looking for him.United States marshals are also searching for Laundrie, and they recently thought they found him -- but then they realized they actually had the wrong man.Read more below.Severin BeckwithSeverin Beckwith and Anna Brettmann, a couple from Ithaca, New York, have been hiking on the Appalachian Trail since September. Once they arrived to North Carolina, they decided to take a break at the Lodge at Fontana Village Resort.Once they arrived, they ate lunch and laid down for a nap. Soon, the door burst open before Beckwith could unlock it and federal agents surrounded the couple, pointing guns at them."Next thing I see is a bunch of guys with riot shields with 'U.S. Marshals' written on them," Beckwith told The New Yorker.Laundrie LookalikeBeckwith told The New Yorker that handguns were "pointed at my face," while his girlfriend was still in bed. A marshal helped her get dressed, as another one handcuffed Beckwith.Still in his underwear, Beckwith realized why this was happening -- he has previously been mistaken for Brian Laundrie, who many believe is hiding somewhere on the Appalachian Trail.Just like Laundrie, Beckwith is skinny and pale, his head is shaved and he has a beard. Still, the marshals were able to tell pretty quickly that they had the wrong man.Severin Beckwith Vs. Brian LaundrieThe marshals fingerprinted Beckwith and he showed them his I.D. They soon realized Beckwith did not have Laundrie's tattoos, then they told him he should think about shaving his beard.But who tipped off the authorities? According to Beckwirth, a day earlier, he and his girlfriend were at the Fontana Lake marina. He asked an employee there to use the telephone, but the employee apparently "responded strangely."That same employee took a photograph of Beckwith and alerted the authorities, thinking they encountered Brian Laundrie.Laundrie ManhuntThe FBI has issued a warrant against Laundrie, charging him with fraudulently using Petito's credit card, but he is not being accused of homicide.As reported by Newsweek, Petito's mother Nichole Schmidt recently accused Laundrie's parents of refusing to cooperate with the police."They know most of the information, I don't know why they're doing this to us. I feel like we need to just know, at this point," Schmidt said."Their actions don't show that their son is missing. It shows that they're just comfortable and they probably know where he is," she added.