Complex sentence: Earlier, residents of the nearby village of Sant'Anna di Stazzema were killed by German forces following a betrayal by a Partisan, named Rodolfo, who knows that Brundt can identify him as the traitor.
Split into simpler sentences: Earlier, residents of the nearby village of Sant'Anna di Stazzema were killed by German forces following a betrayal by one of the Partisans. This Partisan is Rodolfo, who knows that Brundt can identify him as the traitor.