Stick to the facts. No need to embellish. I had my wife do this. I asked her about who, what, when, where & how. I asked her about planning. What steps she took to see OM &get me out me out of the way. Some of her friends were involved and alibied her. Those friends are gone. If you had help in your affair--- an alibi, friend letting you use their place, etc, that friend will be a trigger so they may have to go.
The most important thing is honesty and completeness. Ask Shawn how much detail he wants and give it to him, even though it will hurt. Omissions are like ticking time bombs at this stage. You never know when or where they will go off, but they make quite a mess.