How does Grover react when Percy tells him about the yarn-cutting?

Percy witnesses some old ladies at a fruit stand bring out a pair of scissors, large and apparently symbolic, having previously watched them knitting a pair of what seemed to be enormous, electric-blue socks. He then sees them cut the yarn.
Later, Grover asks Percy what he saw at the fruit stand, and Percy, puzzled by Grover's strange behavior, says that he saw the middle of the three old ladies bring out a pair of scissors and cut the yarn. When he hears this, Grover closes his eyes and makes a gesture which Percy interprets as akin to crossing himself, but not quite the same thing. Nervously, Grover begins chewing at his thumb and says he doesn't want things to be "like last time." He mentions that "they never get past sixth" and asks to walk Percy home. He seems very concerned that something terrible is about to happen.
Percy asks whether this is "a superstition thing" or if Grover thinks somebody is going to die. Grover does not respond in words but "looked at me mournfully, like he was already picking the kind of flowers I'd like best on my coffin."
After this, disturbed by Grover's behavior, Percy leaves him at the bus station when Grover goes to the bathroom.