When an employee is crying at work, your main goals are:...

...One: discretion.

Don't change what you're doing, only what you're saying.

Don't call any attention to the employee.

And two: understanding.

With your words and actions, make them feel like it's normal to be emotional.

Never try to stop someone from crying.

No hugs, but stay professional.

Composure is important.

Ask if they would like to talk later.

If they want to talk now, let them.

And listen.

No, really, listen.

Okay, you can stop listening now.

Seriously, say something.