Kyle met the Palins when helping to consult on security operations for the premiere of a documentary about the former Alaska governor that debuted in 2011. Palin’s husband, Todd, also appeared on an NBC reality series with the Navy veteran.

"We may never know to what extent Chris kept us free or how many lives he saved by his brave actions in the line of fire. But his fellow warriors know how important he was," Palin wrote.

Kyle, 38, served in five combat tours in Iraq and was thought to have killed 160 people during his service. He and another veteran were killed at a shooting range Feb. 2 by a former Marine who was thought to be suffering from combat-related mental health issues.