Indianapolis Lynching

For Juneteenth, here is a scan of a postcard I recently found of Riverside Park Pavilion in Indianapolis.

Front of Postcard, looks innocent enough:

 

But then you read the back and maybe feel sick to your stomach:

 

Since it was never mailed, there is no postmark, and I am unsure of the date or of the lynching referred to therein.

If you cannot read it, it says:

This is where they lynched a negro the other day. They don't know who done it. I guess they don't care much. I don't, do you?

Update: There are some postcards with this one from Indianapolis. They have the same handwriting and are dated 1911 to 1921. They are adressed to Mrs. George Brown, Cedar Grove, IN, and signed, - your son John