I Have Some Concerns Regarding The Death Of My Husband

I have some concerns regarding the death of my husband last Monday he suffered from COPD and sleep apnea he had pain in his neck a week past Friday and was given strong pain relief and diazepam. He took three tablets over 24 hrs as prescribed he felt unwell the following day and was admitted to hospital 24 hrs later he died. I have read that with his condition he should not have been given these is it possible this hastened his death