Eighteen people were killed when a 40-year-old Army reservist opened fire at a bowling alley and a restaurant in Lewiston, Maine.The incident was the deadliest mass shooting of 2023.In the months prior to the shooting, the killer, Robert Card, was in a deep mental decline. He was hearing voices and becoming increasingly aggressive.His ominous behavior disturbed his family, friends, and his military colleagues.More than two dozen law enforcement officials had information about his threats and access to firearms, but no one was able to remove the shooters weapons or stop him from committing the deadliest shooting in Maines history.For the last year, Scripps News has been trying to find out why. Watch this episode of Scripps News Investigates to find out what we've uncovered.