Tisch said Mangione was carrying a “handwritten document” which outlines “both his motivation and mindset” for Thompson’s murder.
Police have not publicly released that handwritten note, nor offered details about its contents.
US media, quoting unnamed law enforcement sources, reported that the note contained the lines, “These parasites had it coming” and “I do apologise for any strife and trauma, but it had to be done”.
Investigators said last week the words “defend”, “deny” and “depose” were written on the casings of bullets found at the scene of the murder.
Many have interpreted the words as a nod to tactics allegedly used by US health insurance companies to avoid paying claims to patients, speculating that Mangione may have acted in anger against the industry.