Card, a 40-year-old military instructor, killed 18 and injured 13 during the October 25 shooting spree in Lewiston, before taking his own life with no explanation.
The Maine mass shooting victims and their families have indicated intent to sue after officials missed red flags - as a probe is launched into the attack that left 18 people dead.
Six days before Robert Card opened fire in the town of Lewiston, he had told workers at Country Kitchen Bakery Outlet that: Maybe you will be the ones I snap on.
In September, Army Reservists were so concerned that Card, 40, was about to kill that they told each other to change the passcode to the entrance gate of their base in Saco and be armed .