God will not force anyone to do good, we have a will to choose and are supposed to seek the good and truth and choose it - murder will only condemn the person acting it out and will need to repent - cancer is caused by sin, and God lets it happen because again, God won’t force anyone to do good, but God can prevent it and can heal and has happened in peoples lives - if I get cancer, may it be offered up to Christ for the conversion of souls - suffering with Christ is better than suffering alone - Christ suffered the most in all history, if we don’t suffer, we also don’t have resurrection, so we Catholics aren’t afraid of death or suffering, we only fear God - so again, may God bless you and guide you more fully to Himself