The actor plays quadriplegic Jackson Walsh in the show, who this week chooses to die with the help of boyfriend Aaron (Danny Miller).
"We always knew what the end was going to be," he told the Boston Herald. "We didn't know how the characters would play out and how well-received they would be. To be brutally honest, the final two episodes are pretty horrific, and we tried to make them that way.
"We don't want one person for a minute to think that [Jackson's decision] is correct. I am an advocate for the idea for the right to die, but I believe the show has covered all the aspects of the storyline and covered all the bases. We're not saying that we believe that this is right; we are showing what these three people believe at the moment.
"We didn't want to glorify it and make it a beautiful thing. That's not reality. In reality, helping someone kill themselves would be a hideous thing, and we try to show that as best as possible."
Spinal injuries charity Aspire recently called the plot "negative, unrealistic and pretty inaccurate".