Image copyright PA Media Image caption Andrew Warren was a senior treasury assistant at Somerville College

An ex-Oxford University employee has pleaded guilty to stabbing and killing a man in Chicago in 2017 - with newly-released court documents revealing details of the crime.

According to a plea agreement released by the court on Thursday evening, Andrew Warren, 58, attacked his victim, Trenton Cornell, while he was sleeping.

Warren and his co-defendant Wyndham Lathem were on the run for eight days before handing themselves in.

Mr Lathem is pleading not guilty.

The pair were charged with six counts of first degree murder. Warren pleaded guilty to the first count and the remaining counts were dismissed.

Warren has agreed to give evidence against Mr Lathem - a former university professor in the US - in exchange for a 45-year prison sentence.

Image copyright Facebook Image caption Hair stylist Trenton Cornell was found dead in July 2017

Mr Cornell, a 26-year-old hair stylist, was found with more than 40 stab wounds on 27 July 2017. At the time, police said Mr Lathem was in a personal relationship with Mr Cornell.

Warren was suspended and then sacked from his job as senior treasury assistant at Somerville College after the body was found, while Mr Lathem was sacked as a microbiology professor at Northwestern University in Illinois.

The court documents allege that Warren and Mr Lathem began communicating online in the month before the murder, after which Warren flew to the United States to meet Mr Lathem.

Around three days later, in the early hours of 27 July 2017, Warren came to Mr Lathem's apartment in Chicago. The pair went into the bathroom where Mr Lathem described to Warren his plan to murder Mr Cornell.

Warren then agreed to video the attack, assistant state attorney Craig Engebretson told a US court on Monday.

The state alleges the pair went into the bedroom where the victim was sleeping. Mr Lathem began to stab him in the face, while Warren allegedly covered the victim's mouth, hit him with a lamp and stabbed him in the chest.

Mr Cornell died from multiple stab wounds.

The killing triggered a US-wide manhunt for the suspects. Warren eventually handed himself in nearly 2,000 miles away from Chicago in San Francisco, while Mr Lathem gave himself up in Oakland, also in California.