My mother-in-law has last stage dementia and lives in an assisted living home. My husband is feeling tremendous guilt for placing her there. Is guilt normal?

At first he would make 2 - 3 day visits. Then it went to 1 - 2 times a month since the facility asked him not to visit so often because she got angry/violent afterwards. She has recently had several seizures and her health is detiorating. It is difficult for him to see her at all. I am now starting to go once a week to visit so that she is not alone. Is guilt normal...and what can be done for it?