
you know, you don't necessarily have to have the hitman leave something behind with his victims, maybe just the style?
for instance, i saw this one show where a professional assassin used an "ice knife". (custom made elsewhere of course.) and it left behind a single massive puncture wound. the hitman would just toss the ice knife away, it would melt, and you have no murder weapon...adds to the mystery, eh? well, maybe something along those lines.
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"If you have nothing good to say...say it often!" -ed the sock
These can be symbolic, leaving a symbol or trinket, taking an important item from the victim or killing with a sentimentaly attached weapon.
Deranged like leaving a pile of feces on the victim, taking their underwear and wearing it home or torturing them to death.
Gloating, purposely leaving a clue as a challenge to the law, a hint of who's going to die next.
Inadvertant, just some weird clue always dropped by mistake.
Novel, like anything that dosn't fit into the other categories.
Since this is a professional deranged calling cards are unlikely, but who knows.
Specific ideas...
Assassin went to prison and kills with his old shiv, jerryrigged in an odd shape or from a unique material that leaves traces in the wound.
A medieval weapon.
An icepick through the ear with the blood cleaned up, one invisible wound, always no sign of struggle. Would take days to determine the cause of death.
Takes trophy fingers/ ears/ tongues.
Takes clipping of the previous murder from the victims newspaper.
Always kills at exactly noon or midnight.
Victims found dead and tied up with police "Crime Scene Evidence - Keep Out" tape, the killer likes to talk to the target before killing and it insults the police.
Only one fingerprint found in the crime scene ,purposely, conspicously placed in ink on the front door.
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We came here to find the American dream. Now that we're right in the vortex you want to quit? You must realize, we've found the main nerve.
-Fear and Loathing in Las Vegas
He could clip their fingernails and take the clippings.
For the more wealthy assasin, he could dress them in the latest fashions from Paris (Just like Ken and Barbie!)
Maybe he's a moonlighting doctor and makes precision scalpel wounds that kill in an instant and leaves behind badly scribbled hints of who the next victim will be. (eh, too Bone Collector)
Maybe he always fixes himself a sandwich out of the victim's pantry.
Whoo, I shoulda been a psycho killer
--Trey
How a bout a knife with a particular pattern etched on the handle?
(I'm not sure, but I think the whole playing card thing in Apocalypse Now was more of a real war thing than a killer thing)
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I once had 509 posts...but now I don't.
Anyway. If letters dont work, why not go to the other extreme. Most of the time, serial killers take a trophy, like a finger or an eyeball or whatnot.
THIS time, why not have the guy only leave a momento, one that is really hard to trace, like a fingernail or tooth ripped out and mailed to the New York Times or something. No name, no note, just a tooth. Then a curl of hair, then perhaps a swath of skin with a partial tatoo on it.
Questions are; is this from the same person? Who could it be, and what do he/she/they want? Or is each from a different one?
Hope it helps
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Okay, who put the stop payment on my reality check???
he he 
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"I am Mars, the god of War, and i'll cut you down".
simple
hit man shoots his victims with some kind of gun, but, hte bullets are made of hidhly condensed ice. The bullet tears through the person, and melts. Therefore, no type of gun can be determined.
or, i read a book called the first deadly sin
really good
the guy uses an ice axe (used for rock climbing, kinda like half a pick axe) to kill his victims with one puncture in the back of the neck.
what about a cross bow
thats origional.
or he dresses up as a loved one and kills them with his bare hands
something creepy and unexpected
maybe he gets a needle in them and puts airbubbles into their blood to make it look like a heart attack?
good luck
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