flags d and e are used when you register event with flag b and not flag a.
DeathMsg is a global event that has to be registered with flag a.
Also, there are never 5 args in that message, that's why i've also removed "5=0"
Also, as it is registered with flag a, no id will be passed, so change :
public overkill(id)
{
with
public overkill()
{
Could be more errors in that plugin, haven't read it much.