AUGUSTA — Robert A. Orr, 53, was shot to death sitting in a chair in his Readfield home Tuesday night before the accused shooter torched the home and fled the state.

That’s the scenario described in an affidavit supporting murder, arson and robbery charges against David B. Silva Jr., 32, who was living at Orr’s home.

The affidavit filed in Kennebec County Superior Court by Maine State Police Detective Jason Richards says Silva had told his girlfriend — Lindsay Spence, who was also living at Orr’s — of his plans to rob Orr after finding a safe, money and guns at the home.

Spence told investigators she woke up to the sound of gunshots Tuesday night, and Silva told her, “Come on. We’ve got to get out of here,” Richards’ affidavit says.

Spence said she saw Orr’s body slouched in a chair “and his head was gone.”

The two drove to Massachusetts in two cars, one of them Orr’s.

Silva, who was arrested Thursday after a brief stand-off in Massachusetts, waived extradition early Friday in a Brockton, Mass., court, and is scheduled to be returned to Maine tonight or Saturday.

His initial court appearance on the charges is set for 8:30 a.m. Monday in the Augusta court.