. >> narration: in collaboration with maine public radio and the portland press herald. an investigation into maine's deadliest mass shooting. >> in e lens of hindsight, i absolutely would have done things differently had i known what was going to happen in october. >> we need to learn more about exposures in the military, not just in combat, but in training. >> this wasn't one breakdown. this was a series of mistakes. and all of these put together put us on the track to lewiston. >> (mouthing) >> narration: now, as part of frontline's local journalism initiative... breakdown in maine. >> frontline is made possible by contributions to your pbs stations from viewers like you. thank you. and by the corporation for public broadcasting. additional support is provided by the abrams foundation, committed to excellence in journalism... park foundation, dedicated to heightening public awareness of critical issues... the john d. and catherine t. macarthur foundation, committed to building a more just, verdant, and peaceful world. more at macfound.org. the heising-simons foundation