"He looked a little disheveled, like he hadn't slept much the last couple of days, but at the same time there was a look of relief," McCloud said. "Relief because of stress, of being on the run for a week."



Lathem's attorney, Barry Sheppard, said he helped facilitate the professor's surrender, and said he expects the man will waive extradition at his next court appearance, likely on Monday. The attorney said he last spoke with Lathem by phone.



"He sounded composed," said Sheppard, whose son Adam Sheppard is also representing Lathem, along with a California-based attorney. He touted Lathem's accomplishments as a microbiologist, and said he doesn't know much about the case other than what's been reported in the news.



"We hope that anyone who reads about the case doesn't have a rush to judgment," he said. "There's a wide possibility of scenarios that could have occurred here."



Lathem was booked into the Alameda County Jail. On Saturday night, Alameda County Sheriff's Sgt. Ray Kelly said he didn't think Lathem was having an easy time in jail.



"He's not doing well, psychologically, in jail," Kelly said. "We're keeping an eye on him."



About 6:30 p.m. Friday, Warren walked into the San Francisco Police Department's Park District station by himself and surrendered, said Officer Grace Gatpandan, a spokesperson for the department. Warren had not communicated with San Francisco officers before he turned himself in to police, she said. He was being held early Saturday without bail at San Francisco County Jail, according to the San Francisco's sheriff's department.



Lathem and Warren will appear in court in California and likely be returned to Chicago, perhaps toward the end of the week, where they will be interrogated by homicide detectives, Guglielmi said. Once the questioning is complete, detectives will hold a press conference outlining the case before the men appear in bond court, he said.



In a statement posted on Twitter Friday night, Chicago police said both men will be held accountable for their actions. "We hope today's arrest brings some small level of closure and justice" for Trenton Cornell-Duranleau's family, police said.



What's yet to be revealed is any alleged motive for the slaying.



Cornell-Duranleau, who had been living in the Heart of Chicago neighborhood, grew up in the small town of Lennon in eastern Michigan. He attended high school in Grand Rapids and earned a state certification in cosmetology in 2011. He moved to Chicago last year, telling friends he got a job at a salon in the city. He was funny and personable, his friends said, and always seemed to find a home wherever he landed, even when he moved to Chicago.



In an obituary posted by his mother, Mischelle Duranleau said her son "loved music and animals. His enthusiasm for life was infectious. Trenton was a caregiver and loved to help others. His youthful free-spirit fueled his love of cars, video games and cartoons."



Police believe he was killed in Lathem's apartment in the 500 block of North State Street around 5 a.m. July 27. But officers were not alerted until an anonymous caller reached the front desk of the building around 8:30 p.m., more than 15 hours later. Authorities found Cornell-Duranleau dead from stab wounds to his back. Blood was everywhere, police said. In the kitchen, police found a knife with a broken blade in the trash can and another knife near the sink.



Police said they suspect Lathem fled with Warren. Both men were seen on surveillance video at the building, police said.



Around 5 p.m. that same day, more than three hours before the body was discovered, one of the suspects walked into the library in Lake Geneva and approached the circulation desk, according to Lake Geneva police Lt. Edward Gritzner. The man told a staffer he wanted to make a donation in the name of Cornell-Duranleau but asked to remain anonymous. The staffer accepted $1,000 in cash from the man, who turned and left through the main door. No one saw him get into the car.



The man did not specify what he wanted the money to be used for, and Gritzner described it as a "general" donation. It wasn't anything unusual for the library.



Authorities have so far offered little information about what may have led to the attack. Lathem and Cornell-Duranleau were involved in some sort of relationship and had "some type of falling out," Guglielmi said. He could not elaborate on the relationship and could not say how Warren knew Lathem and Cornell-Duranleau. Sources say Lathem and Cornell-Duranleau were dating.



Warren, a senior treasury assistant at Somerville College, had disappeared this summer, making the trip to the United States without telling his sister or his boyfriend in Faringdon, Oxfordshire. His friends wonder whether the death of his father in a car crash eight months ago played a role in his behavior. He had confided in them that he was depressed and still grieving.



Lathem was known as a driven scientist whose work on the plague known as the Black Death made national headlines in 2015. He joined Northwestern in 2007 and worked primarily in a research lab within the Department of Microbiology-Immunology at the Feinberg School of Medicine. William Goldman, who advised Lathem as a postdoctoral student between 2003 and 2007 at Washington University in St. Louis, was shocked by the news of the stabbing. He said Lathem was driven by excellence — a model scientist.



U.S. marshals were able to catch up with Lathem while he was on the run because they knew he had friends and family in the Bay Area. Those people said they'd learned Lathem was in the area, but at some point, McCloud said, the lead "went cold." Then it started heating up again. U.S. marshals confirmed Lathem was in the area and a request was made for a "safe surrender."



Lathem was cooperative during his surrender, and did not have anything dangerous on him. While the U.S. marshals explained the process moving forward, Lathem had some concerns.



"How do I get money?" McCloud recalls Lathem asking. "You mean I don't get to eat?"



The marshals explained that he would be fed three times a day, and that he could have money placed on the "books" that he could use for chips or cookies in the commissary. Lathem then asked the marshals to define what a commissary was.



Those types of questions, McCloud said, make Lathem's case unusual.



"He didn't have a criminal history," he said. "Most of the investigations we conduct are (with) people that have histories."



Chicago Tribune's Elyssa Cherney, Rosemary Regina Sobol and Elvia Malagon contributed.



jgorner@chicagotribune.com



meltagouri@chicagotribune.com