Problem: Carlo, a 41-year-old man whose brother was recently murdered is brought by his fiancée to the hospital after showing signs of severe depression. It was also reported that during the past week he has begun to show peculiar behavior and claims that his brother is talking to him. Within 4 days of hospital admission and therapy, he improves rapidly and was able to return to work after 8 days from the onset of his initial symptoms. What could be the possible diagnosis? schizoaffective disorder C. schizophreniform brief psychotic disorder D. schizotypal