Wetting the bed at 8 years old is pretty normal but since it suddenly started it could be due to stress, anxiety and believe it or not too cold of a room can cause a kid to wet the bed.
Make sure his room isn't too cold at night.
You should wake him up in the middle of the night to take him to the bathroom, and have him go pee before going to bed.
You can get him some pampers bed mats that will protect his mattress from the urine at night or get him some goodnites or underjams.
If he continues to wet the bed then it can't hurt to take him to the doctor to have him checked out to be sure it's nothing more serious.