Speaking to Digital Spy at the Monte Carlo Television Festival, McKenzie told UK fans of the show that the partnership between Ben and Sammy in the fourth season is "very exciting", adding that they have "a kind of adrenaline-filled, aggressive style to them".
He also spoke about the upcoming fifth season in the US, promising that there will "absolutely" be repercussions for the shocking end to the fourth run.
Watch Ben McKenzie speaking with Digital Spy about Southland below:
"One of the things we're telling in a larger way on the show across all stories is the way that the job tends to get at you," the actor said. "It tends to break you down, it tends to take you apart piece by piece."
McKenzie continued: "It's always interesting to see on our show how we deal with things because often we don't deal with things directly. Even though they have repercussions, they might be more psychological than they are on the job.
"This might all get covered up on the job, but who Ben is as a person and who he becomes over the next few seasons has already been set. The wheels have been set in motion. I don't think we can go back. Once he's gone down this path he has to continue to go down this path, so I think it's going to be very explosive."
McKenzie also revealed that he is still recognised for playing Ryan on The OC and described that show as "terrific".
"it's nice - you start developing multiple families," he said. "You have the first family you started out with - The OC. Now I have a Southland family. The world just gets bigger and bigger - it's nice."
Southland airs on TNT in the US and on More4 in the UK.