My 11 yr old son ped out from reading a book?

he was in cl and was reading to himself where the red furn grows and he got to a realy gory part and he said he started feeling weird and then he ped out and fell outta his chair.he went to the nurses office.she said his blood pressure was a little high but that was because he was scared.hes totally normal now.but im bringing him to the doctors at 2 pm.im scared is this normal?ive never heard of this happening before.