Professor Wyndham Lathem was arrested by US Marshals in Oakland, California, and Oxford employee Andrew Warren was taken into custody by police in nearby San Francisco, said Ed Farrell, a supervisory inspector for the US Marshals Service. Background on the case may be found here.
When Northwestern officials learned of the murder investigation Monday, they placef Lathem on administrative leave and barred him from campus.
'I've never seen where suspects in a homicide would make a donation in the victim's name, ' said Lake Geneva police Lieutenant Edward Gritzner.
"Whatever the circumstances, we would urge him to contact the USA authorities as soon as possible, in the best interests of everyone concerned".
Lathem, an associate professor of microbiology and immunology, sent family and friends a video in which he apologised for his involvement in the slaying, police said on Friday.
Surveillance cameras recorded both suspects leaving Cornell-Duranleau's upscale apartment shortly after the murder, according to police, and authorities issued warrants for their arrest on Wednesday.
Chicago police said the two will go before an Oakland court and be returned to Chicago.
Lathem and Cornell Duranleau knew each other and had "some type of falling out", Chicago police spokesman Anthony Guglielmi told the Tribune.
"We are also thankful both men are safely in custody and this did not end in further tragedy", the statement said.
Somerville College has confirmed that Mr Warren has since been suspended from his post, which he held at the college for eight years.
On the night of the murder, the front desk of Lathem's apartment building in the River North neighborhood received an anonymous call saying that a crime had been committed in Lathem's apartment on the tenth floor.
Lathem (42) was in Oakland when arrested, while Warren (56) was in San Francisco. They are not sure how Cornell-Duranleau or Lathem knew Warren, or if Warren knew them before he flew to the United States before the stabbing.
On a university web page that has since been deleted, Mr Warren was listed as a senior treasury assistant at Oxford's Somerville College.