Usage patterns
〈事〉の最中にright in the middle of (an event/activity)
The phone rang right in the middle of the meeting.
〈動詞〉ている最中にwhile in the middle of doing something
An earthquake struck while we were in the middle of eating.
〈事〉の最中だto be right in the middle of (something)
I'm right in the middle of important work now, so let's talk later.