The deaths were caused by a Japanese balloon bomb.

Batgirl then pushes Mary into a balloon bomb, killing her.

Unbeknownst to the group, this was a dangerous Japanese incendiary balloon bomb.

The Japanese army built balloon bombs to attack the American mainland.

On January 10 1945, a balloon bomb was shot down approximately 30 miles west of the town.

They were killed by Japanese fugos - balloon bombs.

The balloon bombs were successful and their use was reported in Scientific American in 1849.

About 300 balloon bombs were found or observed in North America, killing six people and causing a small amount of damage.

About 300 balloon bombs were found or observed in America.

It is likely that more balloon bombs landed in unpopulated areas of North America.