The filmmaker's 32-year-old son is charged with two counts of murder in connection with the deaths of Rob Reiner and Michele Singer Reiner.

"From my interactions with Nick, he seemed like a gentle guy," Douglas Shaffer, who worked on Being Charlie as an executive producer, tells PEOPLE. Nick wrote the movie's script with friend Matt Elisofon, based in part on Nick's experiences with drug addiction from an early age, while dad Rob directed the film.

Alan Jackson, the attorney who represented Karen Read, Harvey Weinstein and Kevin Spacey in high-profile cases, is defending Nick Reiner.