Rex Heuermann's 'Best Friend' Details Jail Visit That Left Him Thinking 'He Did It'

David Jimenez is just one of the people interviewed for Peacock's new The Gilgo Beach Killer: House of Secrets docuseries -- out today. In the three-part doc, Jimenez opens up about the pair's friendship and the allegedly chilling visit he made to see Heuermann in jail after he was arrested for a series of brutal slayings.

Rex Heuermann was initially arrested in 2023 and charged with the murders of Amber Lynn Costello, Melissa Barthelemy, and Megan Waterman. Then, in January 2024, he was also charged with the murder of Maureen Brainard-Barnes, before additional murder charges for Jessica Taylor, Sandra Costilla, and Valerie Mack came later in the year. He has pleaded not guilty across the board and awaits trial.

"I'm in a story that I never wanted to be. I'm the best friend of a serial killer," Jimenez says, describing himself in the doc. "It's like I hit the lotto, but I didn't win any money. And not a good lotto."

Per Jimenez, the pair met in 2006 and quickly bonded over architecture and guns; he added the two often went to gun shows together and claimed he got a tour of the so-called "vault" in Heuermann's basement, where he cache of weapons was found. According to Jimenez, he's one of four people who had ever been in the room before authorities.

At one point in the series, Jimenez details an alleged incident at a gun range, claiming Heuermann put a gun in his face after he "touched" a gun while Rex was downrange. Jimenez said Heuermann heard him cock his gun and immediately "pulled out his gun" and started "running to me," putting the weapon in his face.

"I put up my hands, 'Sorry, sorry, sorry, Rex put the gun down!'" he recalled. "He goes, 'You scared the s--t out of me. I thought you were gonna kill me!' It was really scary."

"Thinking back now, I think that was the monster that's hiding in there," said Jimenez. "Rex at home, his family, his wife and his kids, respected him. But I also think, you don't want to piss dad off. Could it be they feared him?"

He later detailed his alleged interaction with Heuermann in jail following his arrest, calling the visit "surreal."

"He says, 'Hi, David, thanks for coming to see me.' I said, 'Rex, this is really bad," he recalled. "I said, 'If you did that, that's another part of you I've never seen. The Rex that I know, couldn't have done that. Everything I hear, it looks like you did it. Convince me, give me something.'"

He claimed Heuermann "had a very visceral reaction" to speculation he possibly killed other women in Las Vegas, before Jimenez brought up the search of his home. He claimed Heuermann said, "They're never gonna find anything there."

"So I said, 'There's so much evidence against you and I don't even believe you, and you're my friend ... come clean, apologize to the victims, don't drag your wife through this. If you did it, confess,'" he said he urged his friend.

"He was really drawn, white, he's an empty shell. You could tell it's a destroyed human being," he continued. "That made me think more that he did it because he's hurt, because he's smart enough to know that that's wrong."

"I said, 'Did you do it?' and then he teared up a little bit and he started crying. I expected to hear, 'David, I'm innocent, can you help me out?'" claimed Jimenez, saying Heuermann instead just looked down. "And that's when I get the feeling, I think he did it."

Jimenez said Heuermann "was a great friend," saying his arrest is "like it's a loss, because he was my buddy."

Peacock's The Gilgo Beach Killer: House of Secrets is streaming now.