User blog comment:Jkphantom9/Volume 3 Episode 9 Preview/@comment-26389992-20160114030502/@comment-26018514-20160114051256

You might if you value the evidence... if he was abusive enough to remove Merc's legs, or conversely loving enough to have them made for a crippled son Marcus would definitely have enough feeling directed at him to ensure his son confirms the kill.

Cinder and Emerald watched the fight, indicating it wasn't a large number of foes, given the fact we see no evidence of other combatants, Merc killing his father is still at least 50% probable.