Wyndham Lathem turned himself in Friday evening in Oakland, California, after authorities made contact with him, while Andrew Warren surrendered to police in San Francisco, according to the US Marshals.
The suspects in the death of Trenton Cornell-Duranleau are now awaiting extradition to Illinois.
Cornell-Duranleau, 26, was found dead from multiple stab wounds in Lathem's Chicago apartment on July 27.
Lathem, 42, is an associate professor of microbiology and immunology at Northwestern and Warren, 56, works for Oxford University in England.
Prior to the arrests, Lathem had sent a video to his friends and family in which he talks about the biggest mistake of his life, a high-level source at the Chicago Police Department told CNN on Friday.
CNN has not seen the video and police are not releasing it, but Chicago Police spokesman Anthony Guglielmi characterized it as Professor Wyndham Lathem "apologizing for his involvement in the murder of Trenton Cornell-(Duranleau)."
His death occurred the same day that one of the suspects walked into the public library of Lake Geneva, a Wisconsin resort city about an hour's drive from Chicago, and made a $1,000 cash donation in Cornell-Duranleau's name.
Victim was 'mutilated,' source says
On Wednesday, Chicago police issued first-degree murder arrest warrants for Lathem and Warren.
Chicago police were tight-lipped about many details. They said they could not elaborate on any possible relationship between the victim and the two suspects.
A high-ranking police official on Thursday told CNN that responding officers found a horrific scene in Lathem's River North apartment.
"The victim was savagely murdered," the official said. Frankly, he was "mutilated."
Police recovered what they believed to be a murder weapon -- a broken blade.
The Cook County medical examiner's office said the autopsy is not complete.
According to CNN affiliate WLS
, investigators determined that Warren had recently come to Chicago from England but didn't know whether he knew the victim.
Police had said they believed the two suspects have fled the state.
"We do have an idea of their whereabouts and efforts to locate them are only intensifying from here on in," police said in an email to CNN. "Our primary focus is to facilitate a safe surrender."
Federal agencies, including US marshals, assisted in the search. Lathem's passport and Warren's travel visa were restricted.
'This place is very safe'
The apartment is in an upscale high-rise called the Grand Plaza Apartments.
"There's shock, there's no doubt about it. You know, this place is very safe," Grand Plaza resident Richard Aili told WLS
. "I've been here 14 years and I've never heard of problems such as that."
Northwestern said in a statement that Lathem "has been placed on administrative leave and banned from entering the Northwestern University campuses."
"This is now a criminal matter under investigation by the appropriate authorities, and Northwestern University is cooperating in that investigation," according to the statement.
Lathem joined the Northwestern faculty in 2007 and researched bacteria that cause disease in humans, particularly lung infections, according to his university biography page, which has since been removed.
He spoke at conferences and has appeared in videos about disease research. One posted earlier this year details how an organism contributed to pneumonic plague
Victim remembered as friendly, a 'character'
A hairstylist fondly recalled Cornell-Duranleau.
"He was a nice kid who got along with everyone. People loved him. He was friendly," Peggy Bosel told CNN.
Bosel has been a hairstylist at Timber's Salon in Trenton, Michigan, for 19 years and said Cornell-Duranleau worked there for around a year and a half.
"He loved people and was really trying to get into the hair business, but that wasn't working out too well. It's a hard business," Bosel said.
She said Cornell-Duranleau was a "character" and had a good sense of humor.
The stylist said she and colleagues had never heard of the suspects.
Cornell-Duranleau left the Michigan salon at least a couple years ago, Bosel said. "He wanted to expand himself and get more experience in the business."