They were told by multiple witnesses who were screaming at SS, “there’s a sniper!”.
https://x.com/sharpfootball/status/1812265909727396107?s=46&t=oXM3QUNDayEotvdo1W-zQA
BBC video: watch from 1m26s to 2m10s - twice mentions SS were on top of a barn, asks why SS weren’t on top of all of the buildings - this is a small place, etc
https://x.com/SharpFootball/status/1812265909727396107/