wayne kyle is the father of navy seal chris kyle - the most lethal sniper in u.s. military history .
kyle was shot dead in 2013 four years after retiring while he was trying to help a fellow veteran struggling with ptsd .
his killer , eddie routh , was found guilty of his murder in february and sentenced to life in prison without the possibility of parole .
his father said the family now has closure following the end of the trial .
a movie about chris kyle 's life called american sniper was released in january starring bradley cooper .
wayne kyle called the movie an ` absolute disgrace ' for the way in which it portrayed his other son , iraq veteran jeff kyle , as ` cowardly '