Sorry for the delay! Things got hectic on my end. 

So for this serial killer, here's what I was thinking: 
-He's sort of a "hired gun" that gets contracted to take down corporations by eliminating the key players within the company. Basically it's a process of eliminating the competition...quite literally xD
-The killer is contracted by a rival corporation to eliminate a separate company from Ujohiri holdings, but the contractor adds a hefty bonus if Ujohiri holdings is destroyed as well, putting a target on Kaz and Juntao along with Ellie, Tyler and anyone else who could be used as witnesses or leverage. 
-We could totally share the killer or one of us could take over full time?