27-year-old Shane Tamura drove across the country from his residence in Las Vegas before opening fire in an NYC skyscraper and murdering 4 people, including an NYPD officer, Monday night.
Law enforcement sources tell TMZ ... he was in Colorado on Saturday and drove through Nebraska and Iowa on Sunday before landing in New Jersey. He was in Columbia, N.J. as of 4:24 PM Monday ... and by 6:28 PM, a 911 center began receiving calls of an active shooter inside a building at 345 Park Avenue on 52nd Street.