The gallows in the picture is a reconstruction of the 1886 gallows and it may not have the trap door as described since it wasn't built to be used.
That’s a great little park and museum in Ft Smith. We spent a morning there several years ago. IMO, one of the more important places in US history, yet remains relatively unknown compared to other ‘Wild West’ locales.
Here’s the actual video.....
Beginning at 2:07
BTW, it’s all there to see and visit atFt Smith National Monument