No, these guys (plural) are not serial killers. They're sending us a sick, twisted little 9/11 message, and I believe the message has been sent, and there will be no more assassinations in this area, at least not for a long while.
I got an e-mail that said 9+1+1=11. 11 people hit. I brushed it off. Maybe I shouldn't be so quick, aye?