American families of victims of the October 7, 2023, attacks on Israel filed a lawsuit on Monday against a prominent Palestinian-American businessman, Bashar Masri, charging that he provided assistance in constructing infrastructure that allowed Hamas militants to carry out their cross-border rampage. The lawsuit, filed in the U.S. District Court for Washington, D.C., is thought to be the first case of a U.S. citizen being accused of providing major support for the attacks that triggered a wider Middle East conflict and upended the region. Masri's office called the lawsuit "baseless."