Actually, I could see INTPs as more likely to snap and blow up one day a la inferior Fe than INTJs who are more methodical and long-term planners. But yeah, it aint relevant. The sociopath card trumps the MBTI card every time.
"There is no god; there is only us. Savage and fragile."
There's no reason to type a murderer. Simply put, the individual isn't human. That same logic applies to 'typing' Hosni Mubarak or the Unabomber in Oklahoma City or the kids from the Columbine murders. We're applying logic to our own prejudice and there's no reason to justify that.