The man accused of killing UnitedHealthcare CEO Brian Thompson in New York is asking supporters to be careful when sending photos to him in prison.

A message on Luigi Mangione's legal defense website warns supporters that every photo is screened by law enforcement. Mangione has asked supporters to send no more than five photos at a time.

The messages and photos are being send to the federal jail in Manhattan where Mangione is held. He receives photocopies of each letter and image mailed to him.

Since his arrest, supporters have raised more than $600,000 for Mangione's legal defense. Billboards proclaiming his innocence have also appeared in lower Manhattan in New York.

RELATED STORY | Luigi Mangione appears in court for the first time since his arraignment

Mangione appeared in court last week for the first time since his arraignment.

He is charged with 11 counts, including one of murder in the first degree "in furtherance of an act of terrorism" and two of murder in the second degree. He has pleaded not guilty to state charges but has not yet entered a plea for federal charges of murder.

If convicted on state charges, Mangione faces the possibility of a life sentence without parole. The federal murder charge carries the possibility of a death penalty sentence.