What should you do if ur boss order you to sack one of your team member without prior notice?

Before taking any action would first need to understand the legal and financial implications of doing this and then would sit with my boss to try and understand the logic behind this decision. As a manager my job is to support my team as much as I can and try to develop them into becoming the most successful people for both themselves and the company. So a decision like this would need to be further assessed before being made