On October 12th, Thursday, President Donald Trump tweeted about the mass
shooting in Las Vegas. He said something like the tragedy last Sunday, but the
tragic incident happened on October 1st.

From my (wrong?) point of view, "last Sunday" at the point of the tweet was supposed
to mean October 8th. But then again, a week starts from Sunday, so October 8th was
this week's Sunday, not last Sunday at the point of the president's tweet?
I'm really confused.

My question is, when you say "last Sunday" on October 12th, Thursday, what date
does it mean?