 Why does the Scorpion leave their signature at each crime?
CALL HIM NEMESIS By DONALD E. WESTLAKE Criminals, beware; the Scorpion is on your trail! The three bank robbers looked like triplets. The third one, who carried a black satchel like a doctor's bag, walked quickly around behind the teller's counter and started filling it with money. The man who had first spoken herded the tellers, Mr. Featherhall and the customers all over against the back wall, while the second man stayed next to Mr. Anderson and the door. Except that in the trunk lid the owner had burned in 'The Scorpion' in big black letters you could see half a block away." "If I'm making just a quick stop—I never spend more than five minutes with any one customer—I always leave the keys in the car.
 To show that they "took care" of each criminal.
 To show that they "took care" of each criminal.  To scare off other potential criminals.  To show that they were present at the crime.  To help lead the police in connecting the crimes.