The mother of a woman who was found dead at Gilgo Beach was killed Saturday, and her other daughter is charged with second-degree murder, police say.

Mari Gilbert, mother of Shannan Gilbert, was killed in upstate Ulster County. Sarra Elizabeth Gilbert, 27, is being charged in the crime.

It is unclear how 52-year-old Mari Gilbert was killed, but her daughter is also being charged with criminal possession of a weapon in the case.

As News 12 has reported, Mari Gilbert had been fighting to find out how her daughter died back in 2010. The body of 24-year-old Shannan Gilbert was found near Gilgo Beach and led to the discovery of 10 sets of human remains in the area.

The original autopsy conducted in the case ruled that Shannan Gilbert's cause of death was undetermined, but the family had an independent autopsy performed that said she may have died of strangulation.

The Gilbert family's attorney, John Ray, says Sarra Gilbert has a history of schizophrenia and has been in and out of mental facilities for years. He says she killed her pet puppy a few months ago, and says she recently bought a knife and took her young son into the woods to "put him to death," but was stopped.

Ray says Mari Gilbert had always been by Sarra's side, and even took custody of her 8-year-old son.

Ray emphasized that the Gilbert family will not give up fighting in the Gilgo case until "a killer is in handcuffs."

Police are expected to give an update on the murder at noon today.