Sarra Gilbert “repeatedly” stabbed her mother Mari Gilbert — whose other daughter Shannan Gilbert’s body was found near Gilgo Beach and whose disappearance resulted in the discovery of 10 sets of human remains — with a 15-inch kitchen knife in upstate Ellenville, according to court documents.

Sarra Gilbert “intentionally repeatedly stab[bed]” her mother with a non-serrated kitchen knife and struck her with a fire extinguisher, causing her death, according to a felony criminal complaint charging her with second-degree murder and fourth-degree criminal possession of a weapon.

The killing occurred Saturday about 10 a.m. in Ellenville, according to the court documents — six years after Shannan Gilbert, a sex worker, went missing. Her body was discovered on the beach in 2011.

Sarra Gilbert, 27, who was arraigned and sent to the Ulster County Jail without bail, is due back in court Tuesday afternoon for a preliminary hearing, police said.

John Ray, who has long served as the Gilbert family attorney related to Shannan Gilbert’s slaying — came to Ellenville Monday and said one of Mari Gilbert’s other daughters, Sherre Gilbert, has asked him to represent Sarra Gilbert.

Ray said he planned to ask the judge to order a psychiatric evaluation for Sarra Gilbert, who he said had been diagnosed as a schizophrenic and had been hospitalized several times in the past year with psychiatric issues. In the days before the killing, Sarra Gilbert was not taking her medication and was “hearing voices,” Ray said, adding that she had been battling family members for custody of her 7-year-old son, who is now with his father’s family.

“She had been hearing voices and these voices were telling her what to do,” Ray said. Mari Gilbert went to check on her daughter when she was killed, he said. “She came to the aid, the assistance of her very sick daughter. This poor girl is a very sick girl. She’s not mentally competent.”

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Ray said he believes the trauma of her sister’s death, had impacted “poor Sarra’s brain and spirit. I am strongly of the belief it affected her mental state and sanity.”

Ellenville Police Chief Philip Mattracion, who declined to comment on Sarra Gilbert’s alleged psychiatric issues citing the ongoing investigation, said the department got a call at 1:45 p.m. on Saturday from one of the Gilbert siblings, asking for police to check on Mari Gilbert’s condition at Sarra’s apartment. When police arrived, they saw Mari Gilbert’s car in the driveway and knocked on the door. When no one answered, they began checking through the windows and one officer saw what appeared to be a body lying on the floor and police moved into the apartment, Mattracion said.

Inside the apartment, Mattracion said, an officer found Sarra Gilbert with blood on her clothing. She was detained and taken to the police station for questioning, police said.

Officers recovered a knife at the scene that investigators believe was the murder weapon, said Mattraction. The medical examiner ruled Mari Gilbert’s death a homicide due to multiple stab wounds, he said.

Sarra Gilbert has a criminal record, according to court documents. She was charged with second-degree criminal contempt after her child’s father, Emmanuel Martinez, reported to police April 28 that Gilbert had violated a temporary order of protection that ordered her to stay away from him and their 7-year-old son, according to Ellenville Village Court records.

Sarra Gilbert called Martinez, 27, on his cellphone and said: “It’s your baby’s momma,” according to the document.

When he told her there was an order of protection in effect, she said “OK” and hung up, according to the document. She was arrested a few weeks later, police said.

She was also charged in February with aggravated animal cruelty and endangering the welfare of a child, according to the Ellenville Village court clerk. Those court papers were not available, the clerk said.

Mari Gilbert had long pushed police on the investigation into her daughter’s death and filed a wrongful-death suit against Peter Hackett, the last person known to have seen her alive before she apparently ran into a nearby marsh from his home. A Suffolk County judge later dismissed much of that suit.

Ray said the legal fight and push for answers about Shannan’s death will continue.

“She was a noble person; she was really a great mother,” Ray said. “She stood by her children in thick and thin. She had a really difficult background situation in her life. She’s a single mother trying to raise all these kids, extremely poor, poverty-stricken woman who always went to work, and always supported her children.”

On the night she disappeared in May 2010, Shannan Gilbert, 24, of Jersey City, made a frantic early morning 911 call from the home of a client, Joseph Brewer, then pounded on Hackett’s door, police have said. Neither man has been charged.

The search for her uncovered 10 sets of human remains that police said may have been the work of one or possibly more serial killers. Shannan Gilbert’s body was found in nearby Oak Beach on Dec. 13, 2011. An officer and his police dog conducting a routine exercise and searching for her stumbled on a body that eventually led to the discovery of a dumping ground of remains along Ocean Parkway.

Since then, Gilbert’s death and the mystery of who killed the 10 others have confounded investigators. They have said her death is not linked to the other victims.

At a 2015 news conference, Mari Gilbert said she was not satisfied with the way police handled the investigation.

“I was very angry, as any parent should be, but as time went by I kind of realized that maybe that was her destiny to help other families,” Mari Gilbert said at the time.

A December 2011 autopsy on Shannan Gilbert’s remains by the Suffolk County medical examiner failed to determine the cause or manner of her death, but an autopsy performed at the behest of the Gilbert family indicated she may have been strangled.