Final answer:
Administer olanzapine.
Step-by-step explanation:
In the acute management of this patient in the emergency department, an appropriate step would be to administer olanzapine. Olanzapine is a second-generation antipsychotic medication that is commonly used to treat schizophrenia. It is effective in reducing psychotic symptoms, including hallucinations and delusions. Since the patient has a history of schizophrenia and is experiencing distressing auditory hallucinations, olanzapine would be a suitable choice for managing his acute psychotic symptoms.