The sources told ABC News it was not clear how close the two sides came to an agreement before the negotiations stopped.
Luigi Mangione's legal team on Thursday withdrew its intention to invoke a psychiatric defense in the state trial over the killing of UnitedHealthcare CEO Brian Thompson.
A carriage horse recently died while carrying passengers in Central Park
Attorneys for Luigi Mangione plan to present an "affirmative psychiatric defense" at his state trial, alleging he was suffering an "extreme emotional disturbance."
Luigi Mangione's next courtroom appearance in New York for his state murder case was pushed back one day due to a paperwork filing delay.