The phrase "first murderer" refers to a person who commits the first known act of killing another human being intentionally and unlawfully. Full definition
His last name, of course, is homophonous with Cain, the biblical first murderer who was cursed by god never to die, which seems a bit heavy handed, considering that he is cast as a murderer on the run. (gamegirladvance.com)
Thus in the Bible, the first city is founded by Cain, the first murderer, who, when left alone after killing his brother cries out (Genesis 4:13), «My crime is too great to bear!» (firstthings.com)
Cain is the first murderer and you wouldn't know that unless you read the Bible on your own and stop listening to him (yes, Cain for fleeing to Nod, area of Russia, and his ancestors that spread the lies of Jesus» truth through history, creating false religions etc. liars of those that don't want you to know God's truth. (religion.blogs.cnn.com)