LOS ANGELES (CNS) - A grand jury indictment was unsealed Wednesday against actor-director Rob Reiner's youngest son, who is charged with murder in connection with the deaths of the famed filmmaker and his photographer wife, Michele, in their Brentwood home.

The indictment against Nick Reiner replaces the case filed last Dec. 16 against the 32-year-old man, who is charged with the slayings of his 78-year- old father and 70-year-old mother, who were found dead about 3:30 p.m. Dec. 14 in the couple's Brentwood home in the 200 block of Chadbourne Avenue between Sunset and San Vicente boulevards.

The murder charges include the special circumstance allegation of multiple murders and a new special circumstance allegation of murder while lying in wait, along with an allegation that he personally used a knife in the commission of the crime.

Reiner pleaded not guilty in court Wednesday and is due back Sept. 15 for a pretrial hearing.

Los Angeles County District Attorney Nathan Hochman told reporters outside court earlier this year that his office will be "looking at all aggravating and mitigating circumstances" and that Nick Reiner's attorney has been invited to present written and oral arguments before a decision is made on whether to seek the death penalty.

"It will be subject to not only a rigorous analysis, but many of the most experienced individuals in the D.A.'s Office with death penalty experience will be helping me evaluate that information," Hochman said.

Nick Reiner had been awaiting a hearing to determine whether there was enough evidence to require him to stand trial, but the grand jury indictment allows the case to proceed to trial more quickly.

The L.A. County Office of Medical Examiner classified the couple's deaths as homicides, with both dying from "multiple sharp force injuries."

The death certificates note they were killed "with knife, by another."

Nick Reiner was arrested by Los Angeles police in the Exposition Park area near USC less than six hours after his parents' bodies were discovered. He remains behind bars without bail.

Los Angeles Police Department Chief Jim McDonnell declined soon afterward to provide any details on what led to Nick Reiner being identified as the suspect.

In a statement released the day of their brother's initial court appearance, Nick Reiner's older brother, Jake, and younger sister, Romy, said, "Words cannot even begin to describe the unimaginable pain we are experiencing every moment of the day. The horrific and devastating loss of our parents, Rob and Michele Reiner, is something that no one should ever experience. They weren't just our parents; they were our best friends.

"We are grateful for the outpouring of condolences, kindness, and support we have received not only from family and friends but people from all walks of life," the two said. "We now ask for respect and privacy, for speculation to be tempered with compassion and humanity, and for our parents to be remembered for the incredible lives they lived and the love they gave."

Rob Reiner was best known for his iconic role as Archie Bunker's liberal son-in-law Michael "Meathead" Stivic on the classic sitcom "All in the Family" -- a role for which he won two Primetime Emmy Awards, along with being the director of films including "Stand By Me," "The Princess Bride," "A Few Good Men," "Misery," "This Is Spinal Tap" and "When Harry Met Sally."

According to multiple reports, the couple's 28-year-old daughter discovered her father's body. One report suggested that a massage therapist had shown up at the couple's home for a pre-scheduled appointment but got no answer at the door and contacted their daughter, who went inside the home and found Rob Reiner slain. She contacted authorities, who subsequently found Michele Reiner's body in the house.

Rob and Michele Reiner, along with Nick, attended talk-show host Conan O'Brien's Christmas party the night before, and sources said Rob Reiner and his son got into a heated argument over his son's odd behavior at the event. Rob and Michele Reiner wound up leaving the event, but it was unclear when Nick Reiner left. TMZ reported that Nick Reiner checked into a Santa Monica hotel around 4 a.m. the next day, and that blood was later found in the room.

It was reported in December that Nick Reiner had been diagnosed with schizophrenia and was taking medications that made him "erratic and dangerous."

Citing two sources with knowledge of the situation, TMZ reported that he had been under the care of a psychiatrist for mental illness, but that his behavior had grown more alarming in recent weeks.

Nick Reiner has been open about his struggles with drug abuse over the years, even working with his father to produce a 2015 semi-autobiographical movie titled "Being Charlie," based on Nick's drug-addiction issues and the family's struggles to cope.

In media interviews and podcast appearances, he previously described being in and out of rehab programs throughout his teen years, and spending time homeless in various states, including Texas, New Jersey and Maine. He also described an instance when he was high on cocaine for multiple days and trashed his parents' guest house.

Rob Reiner -- who was married for 10 years to actress/director Penny Marshall before they divorced in 1981 -- married Michele Singer in 1989 after meeting her while he was directing "When Harry Met Sally." Reiner often told the story about how his romance with Singer led him to change the ending to the movie -- with the characters played by Billy Crystal and Meg Ryan reuniting rather than going their separate ways.

Rob Reiner was a vocal Democratic Party activist, helping to spearhead efforts to legalize same-sex marriage in California and to pass a 1998 initiative that created the First 5 California childhood-development services program, funded by a tobacco tax.

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