This was your question, no? I answered and responded to your question; Did you not think there is a possibility more than one object was thrown? Which would mean they were all doing it at the time, but only one found it's mark.
And since you implied you already knew the answer to your own question, then it was you who answered your own question, not I.
My actual reason for asking was to point out the odd wording mostly by the author of the piece..
The article makes it sound as it all for dropped one sandbag and that one ,and only one, sandbag killed the passerby.