Are erflies a sign of death?

I am not the least bit superstitious but my friends mother asked me to research something for her. She was telling me how last spring/summer of 2009 she noticed an occurrence in her backyard. The previous owners had kept up a garden and you can still see the rectangular shape of where the garden used to be. On this day last year she was walking out to her car and happened to look into the back yard. Right above where the garden is she saw thousands of white erflies and some other colors, but mostly white, hovering over this patch of rectangular gr. She was very surprised and tried to get her son and husband to come look but they were too busy. She never saw them again and wasn't sure why they appeared but about a week later one of her 2 dogs died. And then a couple weeks after that her other dog died. and at the end of the summer, her husband ped away. We were wondering if any of those ties could be because of the erflies or if not why were the erflies hovering over the garden patch? There aren't any flowers or weeds where this garden was so I can't think of the reason the erflies would be there? If anyone knows anything please let me know! and don't be a smart please. thank you.