Hallowe'en Fancy Dress - with Tragic Footnote

As far as is possible with fancy dress, I am estimating that this photo dates from the 1930s, given the padded shoulders on some of the ladies' dresses.  It could also be 1940s.  The location could be a private house or a village hall, there are few clues one way or another.  On the reverse is written:
"Halloween.  These are a few of our Association.  The one marked with a X was instantly killed last week and was the President."

Fancy Dress - Medieval; Cavalier; Romantic

  I think that these photographs are all studio portraits of people dressing up or amateur actors, rather than the official postcards featuring famous actors which were sold.

On the back of this last one - which I think is the latest of the four - is written 'Lottie, taken on March 8th, '30'.

Fancy Dress Ball on Roller Skates c.1910s

I would love to know who these people are; where this was taken; when it was taken (though I am guessing a date of c.1910-1920) and whether everyone was wearing roller skates or just the people in the front rows.  The costumes and decorations are fantastic.  I wondered if the event is not a ball, but a theatrical production of some kind, which still doesn't make the role of the roller skates any clearer.