New to grand mal seizures

My husband of 19 years had a grand mal seizure 2 weeks ago in his sleep. It was a very violent seizure and he stopped breathing for a bit. He had a real hard time coming out of it. At the time I did not know it was a seizure I thought it was a heart attack. After I he stopped breathing I called 911 since I could not revive him. I have since read all the things you should and should not do during and after this type of seizure. I did all the wrong things. My husband was out of it for 2 1/2 days after. He was just not there mentally and slept around the clock unable to work at all. The following days were a little better but he still was so sleepy. He was put on Depakote. He does not remember the whole week after his seizure. My husband had a massive head injuy 26 years ago. He had CAT scan, MRI and EEG, looks like it was this injury that caused his brain to reconfigure itself. I am shocked that 26 years later it decides to do this??? Does anyone know of the chances of having another grand mal seizure once you already had one is?