Michael Royce Sparks, 62, was charged with two counts of murder and two special circumstance allegations.
"From the beginning of this case, what we were impressed by were the community members, the friends and loved ones who learned about the Menards and came forward to indicate that things weren't right," said San Bernardino County District Attorney Jason Anderson during a Tuesday news conference.
Sparks is expected to be arraigned on Wednesday. With those charges, the DA could decide to seek the death penalty.
According to Redlands Police Chief Rachel Tolber, a family member told officers Sparks had admitted to killing two people.
"It was while our teams were on site that the police dispatcher received information from an individual identified as a family member indicating that [Sparks] was involved in the disappearance and had admitted to killing two people and was threatening suicide," said Tolber.
He was arrested late Thursday, days after Stephanie Menard, 73, and Daniel Menard, 79, were reported missing from their home in the Olive Dell Ranch nudist resort.
Authorities concluded their search for the couple at Sparks' home after recovering human remains from the property.
Police had returned to the home on Monday but by the afternoon reported that all personnel have cleared the search scene. The site is now fenced off for public safety and code enforcement is expected to red-tag the property Tuesday.
The Menards and their dog were last seen Aug. 24, and authorities quickly mobilized to find them.
Arrest made on street in nudist ranch stormed by SWAT in search for missing Redlands couple
Sparks was booked at the West Valley Detention Center in Rancho Cucamonga.
He surrendered voluntarily after he was found underneath his home, which was torn down by a police armored vehicle with a hydraulic battering ram.
"He did have a rifle and he did attempt to kill himself when police discovered him," said City of Redlands spokesperson Carl Baker. "The weapon misfired ... it didn't go off."
Authorities believe the Menards are dead.
On Friday, human remains were found in bags in what authorities described as a concrete bunker underneath Sparks' home. Police continued their search Sunday and recovered additional remains.
The remains have not been identified but officials believe they likely are the Menards.
The motive for the alleged killings remains unclear, but the community is heartbroken. They held a vigil over the weekend to remember the Menards.
"They were always together," said neighbor Tammie Wilkerson. "He was so sweet, gentle and always was concerned about everyone else."
She says it was clear the couple and Sparks hated each other. It likely started with a dispute over a pepper tree. Dan Menard asked Sparks to trim it and when he refused, Menard cut it himself, Wilkerson said. But there were probably other conflicts as well, she said.
Vigil held for missing Redlands couple believed to be dead