MobLand Episode 9: Why Did Kevin Kill [Spoiler]?

In MobLand Episode 9, Kevin (Paddy Considine) kills former prison guard Alan Rusby (Nigel Lindsay) to exact his long-awaited revenge. After an emotional breakdown, Kevin initially spares Rusby despite holding him at gunpoint. However, when Rusby returns to offer comfort, Kevin fatally shoots him in the head, delivering the instant death he’d been planning all along.