Nick Reiner was seen casually strolling by a gas station close to his parents’ luxurious Brentwood home just hours before they were tragically murdered.

Surveillance footage obtained by The Post reveals the 32-year-old screenwriter dressed in a laid-back manner, sporting jeans and a long-sleeved shirt, with a backpack slung over his left shoulder.

He was captured on video moving away from the direction of Rob and Michele Reiner’s residence, shortly before midnight on Saturday.

The gas station is a mere few blocks from the home of the acclaimed “Princess Bride” director and his spouse, as reported by the outlet.

The incident took place just hours before his parents were found fatally stabbed early Sunday morning, according to the Los Angeles County District Attorney.

Insiders divulged to The Post on Monday that Nick allegedly “freaked out” during an argument with his parents at Conan O’Brien’s star-studded holiday bash on Saturday.

“They had had an argument at Conan’s holiday party, and Rob had been telling people that they’re scared for Nick and scared that his mental state was deteriorating,” a Reiner family friend told The Post.

The source also alleged that Nick was “badly addicted to a combo of opiates and heroin” as he battled a years long history of drug use and violent behavior.

Nick also allegedly had a tense moment with “Saturday Night Live” alum Bill Hader after allegedly interrupting a conversation at the party, according to NBC News.

An insider told the outlet that Hader explained to Nick, 32, that he was having a private conversation. Nick was said to have stood motionless and stared at the comedian before “storming off.”

Hader emerged Tuesday in Los Angeles for what appeared to be a strained phone conversation.

Rob and Michele were found stabbed to death in their home on Sunday afternoon with daughter Romy, 27, discovering their bodies, according to The Post.

The “When Harry Met Sally” director was 78 and his wife was 70. They also shared adult children Jack, 34, as well as Reiner’s adopted daughter Tracey, 61, from his previous marriage to Penny Marshall.

Romy allegedly told police at the scene that a “dangerous” relative “should be a suspect.”

Police arrested Nick on Sunday evening at a downtown Los Angeles Metro station, with dramatic footage of the arrest emerging on Tuesday.

Nick is currently being held without bail at downtown Los Angeles’ Twin Towers correctional facility after being transferred from Parker Center Jail. Per sources for TMZ, Nick is on suicide watch.

Los Angeles County District Attorney Nathan Hochman and Police Chief Jim McDonnell explained during a press conference on Tuesday that Nick will be charged with two counts of first-degree murder.

“These charges will be two counts of first-degree murder with a special circumstance of multiple murders,” Hochman told reporters.

“He also faces a special allegation that he personally used a dangerous and deadly weapon, that being a knife.”

Nick faces the possibility of the death penalty or life in prison without the possibility of parole, and Hochman said the Los Angeles County District Attorney’s Office will take the “thoughts and desires of the family into consideration.”