Philip Markoff has been put on suicide watch after the 26-year-old suspected "Craigslist Killer" was found with shoelace marks around his neck in what may have been an attempt to take his own life. 

ABC News reports:

Markoff was moved from the general population of Boston’s Nashua Street jail to a segregated unit where officers can keep a constant eye on him, sources said. The move was made because ‘shoelace marks were found on his neck,’ law-enforcement sources said. Markoff’s attorney, John Salsberg, visited the inmate today, but declined to discuss whether Markoff tried to commit suicide.

Markoff was arrested and charged on Monday with the murder of a New York masseuse, Julissa Brisman. He may also face charges in the robberies of two other women who were contacted through Craigslist.

While Markoff may have tried to end his life on Thursday, more startling details of his dark side came to light. Morgan Houston, a friend of Markoff, shared a scary confrontation she had with him in college. Police also said they found a victim’s underpants in Markoff’s home.

Click here for the full ABC news report.