The gunman who killed two Virginia television journalists on air had planned the assault well and identified with mass murderers and the Sept. 11 attackers, authorities said on Friday.

The shooter, Vester Lee Flanagan II, gave no sign of his destination or next move when he fled after gunning down the journalists from the Roanoke station WDBJ on Wednesday, the Franklin County Sheriff's Office said in a statement.

"It is evident that Wednesday morning's attack was well-planned and premeditated" and Flanagan apparently acted alone, the statement on the shooting investigation said.