When investigators found the bodies of two teenage girls near a trail in Indiana in February, they extracted two mysterious clues from one of the girls’ cellphones: an image of a man behind them, his head down and hands in his pockets, and a recording of a voice ordering the girls to the place where they died with the words “Down the hill!”

Five months have passed, and the murder of Liberty Rose Lynn German, 14, and Abigail J. Williams, 13, in a wooded area near Delphi, Ind., remains unsolved.

But this week, investigators have new hopes for solving a double murder that the state police chief has said is proof that “evil lives amongst us.” On Monday, the authorities released a composite sketch of a suspect and a description: 5 feet 6 inches to 5 feet 10 inches, weighs 180 to 220 pounds, and has reddish brown hair. By Tuesday, they had 500 new tips, according to the F.B.I.

“It is a lot,” Sgt. Kim Riley, an Indiana State Police spokesman, said in an interview. “We had been averaging between five and 10 a day.”