Describe each step you will take to manage or resolve this example of workplace conflict?

Workplace conflict is common and likely to happen whenever people are asked to work together.  For the scenario below, you are the manager of the two direct reports described in this scenario. 

An employee in your department (Sarah) who has always performed at the highest level, communicated effectively with team members, and is a strong candidate for promotion recently became more reserved in her office interactions, is coming in early, and working late - but just does not seem to be herself.  You've asked her if everything is okay and offered resources, but she indicates everything is fine in your discussions. 

While making copies in the copy room, you hear part of a conversation between a newer employee (Sam) and what appears to be a representative from one of Sarah's top sales accounts. You are not concerned as it is common for team members to help each other out during busy times of the year. 

A few days later at the monthly team update meeting, there is obvious tension between the two employees. As team member share their progress, successes, and sales numbers going around the room - Sam mentions how great he's done for the past few weeks. Sarah gets up and leaves the room, obviously upset. Sam smiles, but does not say more. 

Describe each step you will take to manage or resolve this example of workplace conflict?