Bill Pullman thinks he was the last person on earth who hadn’t heard of Alex Murdaugh, the personal injury attorney who was found guilty in the double homicide of his wife, Maggie, and son Paul.

Fortunately for the veteran actor, there was gobs of video to help him prepare for his role in Murdaugh Murders: The Movie for Lifetime‘s ripped-from-the-headlines slate of movies last fall.

“South Carolina allows video in courtroom. There was hours and hours of behavior, that 911 call, the body cam of the first officer arriving on the scene,” Pullman recalled Saturday at Deadline TV Contenders. “It’s really interesting about real transcripts. You realize how sociopaths have this cauterized morality. The way they are moving through a sentence. They talk one way at the beginning at the sentence and then they sense there is somewhere better to go. You would never write that as a writer. You can get a lot into the psychology by the syntax they use…things aren’t polished.”

Pullman had only six days to prepare for the role before production began (the film was shot in six weeks right before the writers and actors went on strike). “I was nervous,” Pullman recalled about doing the movie that was written by Michael Vickerman and directed by Greg Beeman. “How are we going to do this?”

But he remembers how that conversation helped him to get into Murdaugh’s head. “I think Alex loved his wife and his son. How do you kill someone that you love? How does that happen? It doesn’t occur to you up until the time you do it.”

“The moment when he took the stand, that was a bad mistake,” Pullman said of Murdaugh’s trial. “He was so certain that he could really talk and the jury would hear. All you need is one.”