Not a serial killer, but a seriously greedy ransomware program that demands a ransom of 13 bitcoins and cripples Windows recovery functionality.  Bleeping Computer report here. [January 2015]

[27th April 2016] However, a subsequent version or variant announced by Mosh has been reported at Bleeping Computer – The 7ev3n-HONE$T ransomware encrypts and renames your files to R5A. This rebranded version demands a more moderate 1 bitcoin ransom. There is no way to decrypt files for free at present. The distribution mechanism and encryption method are not currently known. Encrypted files are named according to the pattern [sequential number].R5A. Commentary by David Bisson for Graham Cluley’s blog: 7ev3n ransomware alters name, asks for much lower ransom.