I'm so sorry you had to experience that. I also watched my daughter have a seizure from a high temperature brought on by her MMR shots when she was a little over 1yr old. It's one of the scariest, heart-breaking, tramatizing things a parent has to see their child endure. I was at work and she was at her grandma's...my mother called me telling me that she was really hot and her eyes were all glossed over and she just was laying there. I raced home, got her to her doctor where she had the seizure within minutes of arriving. I thought she was dying before my eyes.
Her doctor told me that certain young children are more susceptible to having seizures because their body doesn't know how to handle the fever yet. Her's lasted almost 5 minutes, and she was fine after it happened. Her doctor told us to monitor her to make sure if she ever got a fever over 102, to immediately put her in a tepid bath, and try and give her some cool fluids to drink to start getting her fever down. Also, MOTRIN is the best for a fever. To monitor a fever to make sure it stays at bay is to switch from Children's Tylenol & Children's Motrin every 3-4 hours until the fever is broken. Trust me, I was on HIGH alert anytime she had any kind of fever because I never wanted her to have to experience that again.
Eventually, children grow out of that danger and their bodies learn to handle the fever.
I would suggest talking to someone about it or doing research on a medical website where you can ask questions about this issue in order to feel ok about it and calm yourself. My daughter never had another seizure, and I was very pro-active in making sure she didn't by taking all the right precautions. I always had Motrin and Tylenol with me at all times, and when ever I noticed her not acting like she felt good, I was on top of her fever before it had a chance to spike. I also made sure any caregiver knew what happened and new to monitor her closely.
Also, some people don't know this...when someone has a fever, it makes them feel cold and have the chills. It's hard to put your child in a tepid bath when he/she has goosebumps...but it's worth it so they don't have another seizure. Also, after the bath, dress your child lightly (even if he/she's cold) and only cover them with something as a light as a sheet. DO NOT let them wrap in a blanket. You probably already know this, but it's surprising how many people don't.
I'm a 29yr old mother of a gorgeous, active little 2-1/2 year old little girl. We have another baby on the way...
Best of luck to you! Don't worry...just make sure if your child is sick before bed, either give him medicine before bed for the fever, or check him through out the night to make sure he's not heating up (maybe have him sleep with you if he's not feeling well so you'll know if he gets a fever). That was my daughter's favorite time to get a fever! In the middle of the night!!