Would you like to be alone or would you need a caring shoulder when you're sad and crying?
I guess the needs of individuals are different.
If a person is crying, it would be
best to leave the person alone, and let the person have his/her own space. Allow the person to cry all out and give him/her time to calm down. Stay by his/her sides to prevent any unforeseen incidents and give him/her moral support.
Don't be upset if they reject your care and concern, as everyone needs time and space sometimes. Let the person know that you will be there for him/her.
Things will slowly calm down and subside. As most things in life, are temporary.