When Tae Bum Yoon got off the train at Portland's Union Station and homicide detectives slapped handcuffs around his wrists last week, his only question was: "How did you find me?''

Yoon, according to court records filed Wednesday, left a long trail that would tie him to 25-year-old Ashley Benson, discovered strangled to death early Dec. 26 in an eighth floor stairwell of the DoubleTree Hotel in the Lloyd District.

She was found wearing black pants and a white shirt just inside the stairwell door, with no socks or shoes on, according to a search warrant affidavit. The medical examiner's office believed Benson's attacker strangled her with his hands sometime between Dec. 25 and 26, according to search warrant affidavits.

The court records reveal Benson was working as an escort and had met Yoon at the hotel for paid sex. It wasn't the first time they had met, and evidence suggests they had some type of disagreement over money owed, the records indicate.

Search warrant affidavits, written by Portland and Bellevue police and filed in King County Superior Court in Seattle, give this account of how Portland investigators tracked down Yoon:

Detectives learned Benson had gone to meet a man in DoubleTree's Room 715 on Christmas. Yoon had checked into the room that night under a reservation made by another man with a similar-sounding name: Chris Youn, a DJ who was expected to arrive the next day with his fiancee.

Tae Bum Yoon showed up at the hotel's front desk about 9 p.m. on Christmas and pretended to be Chris Youn. He said he wanted to check in earlier and asked if he could have the same discounted rate. He showed the front desk clerk a Washington license with a Bellevue address, and gave her a phone number and email address. He had the hotel change the reservation to match the spelling of his name and paid in cash.

Police found that multiple phone calls had been made from the DoubleTree's Room 715 to a Washington phone number with the area code "360.'' A detective did a Google search on the phone number and found it listed in ads for an escort service. The ads on websites of "EscortProfile" and "TNA.com" and "backpage.com" showed photos of a woman matching Benson under the name "Foxxy. Veronica.''

Her ads read, "I am the PERFECT COMPLETE package. Sxxy, Freaky & Sweet.''

The day Benson's body was found, police obtained a judge's signature, allowing police to track through GPS the location of the cell phone with the "360" phone number. On Dec. 28, members of Multnomah County's search and rescue team found Benson's phone. Court records did not identify the location. The cell phone revealed Benson had received an email to "sexy.veronica@yahoo.com'' from the email address of chrisyoon1990@hotmail.com.

The email said: "Let me make this clear before you read my message. You WILL be COMPENSATED for all the time you invested in me. I have every intention of PAYING you...Before you blame me 100 %, I want you to know that you did break our agreement. You did post and although I forgave you, I did find new listings in Houston texas backpage.''

Portland detectives contacted police in Bellevue on Dec. 30, asking them to keep watch on Yoon's residence. Police had determined that Benson and Yoon had met at the DoubleTree on Christmas for paid sex and had prior encounters. Yoon left the hotel and Benson's body was found.

Investigators also talked to Marcus Depree Giles, 29, who said Benson was his girlfriend who lived with him. Giles knew Benson had met a man by the name of "Chris Yoon,'' and Yoon had paid her for the dates, and also had given her a large amount of money "for doing nothing at all,'' an affidavit says.

Bellevue police initially had the wrong address, but soon figured out that Tae Bum Yoon, who also often went by Chris Yoon, was living in an upscale apartment building called TEN20 at 1020 108th Ave. NE, where the rent was about $3,000 a month, according to court records.

Meanwhile, Portland detectives got a warrant to track Yoon's iPhone 5 and "ping'' the phone for its location. On Jan. 6, the pings showed his phone in Federal Way, Wash. By the next day, the phone pings showed he was back in Portland. Detectives confirmed with Amtrak that Yoon had taken a late train and was in the area.

Yoon was arrested on the afternoon of Jan. 7 at Union Station. A further examination of his cell phone, seized upon arrest, revealed multiple images that suggested he was heavily involved in cocaine trafficking, according to Multnomah County and Washington state court records. The photos included bags of cocaine, shipping containers addressed to people in multiple states and one photo of a computer screen showing an order for "White stallion's flame cocaine, all rock.''

Bellevue police conducted a search of Yoon's apartment and found further drug evidence, according to court records. In a hallway laundry closet, police found a quart-sized plastic bag containing cocaine, digital scales and a small black safe with cocaine residue, according to a search warrant affidavit. In a master bedroom, police found a cutting agent for cocaine, Inositol, and postal service shipping receipts and labels throughout the unit.

"Cocaine trafficking would explain how an individual with no visible means of support or job might afford the rent at the TEN20,'' Bellevue Officer Greg M. Grannis wrote in a search warrant affidavit.

During an interview with Portland homicide detectives, Yoon was vague about when he started setting up dates with Benson. He told police he first called her because it was difficult for him to meet women, the affidavit said. He said he first met her about three or four months earlier. On Christmas Day, Yoon had sent or received more than 25 text messages from Benson, and called her phone twice.

Immediately after the killing, police suspect Yoon ran to another hotel, the Residence Inn at 1710 N.E. Multnomah St. There, a clerk recalled him arriving early Dec. 26. He was sweaty and bleeding from multiple scratches to his face and neck, a Residence Inn clerk told police. She asked him what had happened, and he told her he'd had a fight with his family and needed a place to be away from them.

Because the inn wouldn't take cash, the clerk called a cab for him. Radio Cab was sent at 2:06 a.m. Dec. 26 to pick Yoon up, and dropped him at the Rodeway Inn in Beaverton.

As Portland police were investigating Benson's homicide, the real Chris Youn arrived at the DoubleTree to check in on Dec. 26. He told police he was a DJ from Bellevue and had come to Portland for a performance the night of Dec. 26.

Youn told police he had no idea how someone else had known about his reservation, but he denied checking in early. He had been at home on Christmas and had photos of him in Bellevue that day to prove it. Youn cooperated with police, who detained him at the hotel. He let police search his cellphone and even allowed police to take DNA swabs from his mouth. He also gave detectives the name of his fiancee, who was with him at the DoubleTree. After interviews and searching the Washington motor vehicles database, Portland police concluded Youn was not the man they wanted.

Tae Bum Yoon remains in custody at the Multnomah County Detention Center on a single murder allegation. Based on court records, he's expected to face additional drug and identity theft allegations when he's set to return to court next Tuesday.

--Maxine Bernstein

mbernstein@oregonian.com

503-221-8212; @maxoregonian