Unfortunately for Bob, the vixen who was in love with Mr. Fox didn't want to be obsessed with. She didn't want to be found, rather. She was a secret agent for the Russian government and former KGB, comrade.
So when she got wind of Bob being obsessed with finding out who she was (yes, she had telepathic informants, wut), she sent one of her underlings to 'silence' Bob.
Or rather, she send five underlings, who had already set themselves up in strategic, hidden sniping points before Mr. Fox had flung the final candy wrapper at Bob.
"And he just wants to open up a coffee shop in Van Ives," chuckled one comrade to another, mounting his scope on top of his sniper rifle as the other took aim.