Citizens Plugin help

My guards will not attack anything! Unless if a player hits him. But he won't attack mobs even if I try the skeleton shooting thing.
Here is what I do.

/npc create Bob
/toggle guard
/guard bouncer
/guard radius 15
/guard aggro
/guard af -m spider or /guard addflag 1 -m spider

But when I spawn a spider he stands there and does nothing. Help please!