In this situation, the most appropriate step with the least invasive method would be:
Asking the caller if they would distance themselves from the knife and pills while you hear what has led them to this point.
This option allows you to create a dialogue with the caller, prioritize their safety by encouraging them to remove immediate means of self-harm, and potentially understand their feelings and situation better. It's important to show empathy and provide support without escalating the situation further. However, it's crucial to also consider involving emergency services or a mobile crisis team if the caller remains in crisis.