On Monday and Tuesday, PBS will devote most of its prime-time schedule to a two-night event built around the theme “Armed in America” as part the service’s ongoing coverage of gun violence. Two films under the “Independent Lens” banner will air, followed by town hall discussions moderated by former ABC News correspondent Michel Martin (now weekend anchor of NPR’s “All Things Considered”). (Both town halls were taped April 27 at Northland Church in Longwood, Florida.)