The idea that
Ted Bundy went into trance like states during his killing sprees
is an anecdotal observation which can be true or it may be false. If we are to be considering it to be true, you could say that what is being described is a severe pathological form of dissociation or compartmentalisation.
I covered the idea of compartmentalisation in a totally unrelated question whereby;
Compartmentalisation is often employed, for example, by people within the emergency services (fire officers, paramedics, police officers, coastguard etc.) in order for them to concentrate on the immediate task whilst temporarily isolating themselves from their emotions.
Compartmentalisation is a form of dissociation in a sense because dissociation is a psychological defence mechanism (Cardeña, 1994) which helps the person to get through the situation with as little harm as possible. The difference between compartmentalisation and dissociation is that when you are compartmentalising, you are very much aware of what you are doing.
So in conclusion
What is being described fits the description of dissociation but it would have to be a severe pathological form of dissociation.
If Ted Bundy did have real empathy, dissociation would have helped him to disconnect from conscious reasoning and empathy with what he was doing. During the state of dissociation, you can appear to be in a trance because you are "throwing a switch on conscious awareness" so that you cannot connect with the event alone at any time after the event.
Cardeña, E. (1994) The domain of dissociation. In: Dissociation: Clinical and theoretical aspects, Edited by: Lynn, S. J. and Rhue, J. W. 5–31. New York, NY: Guildford Press.