Even as Brooke Astor lay on her deathbed, a feud between her son and her friends raged, culminating with a butler summoning guards to stop Astor’s daughter-in-law from witnessing the last rites.

Details of the 105-year-old Astor’s final days and the enmity between those closest to her are emerging in filings at Surrogate’s Court in Westchester County, where the late philanthropist’s fortune is being divided.

The two main opponents in the dispute over Astor’s estate are her longtime friend Annette de la Renta and her son, Anthony Marshall. The rift between them surfaced publicly last summer when Mrs. de la Renta backed claims that Mr. Marshall was depriving his mother of proper medical care and amenities such as fresh flowers.

Although a judge found the claims unsubstantiated, guardianship of Astor was transferred to Mrs. de la Renta and a bank, JPMorgan Chase, from Mr. Marshall, a theater producer and former ambassador. Since then, Mr. Marshall says in court documents, Mrs. de la Renta has been “my mother’s gatekeeper.”

The dispute over access to Astor did not end even as those closest to her gathered in the days before her death, which came Monday of last week. When Mr. Marshall and his wife, Charlene, rushed to Astor’s bedside two days before her death for the administering of the last rites, Mrs. Marshall was denied entry to the house by security guards acting at a butler’s urging, Mr. Marshall declared in an affidavit. Mrs. de la Renta, who was present at the scene, refused to intervene on Mrs. Marshall’s behalf, according to the affidavit. The last year, Mr. Marshall wrote in a filing, “was truly the worst year of my life, and that’s saying a lot (I’m 83 years old.)”

One visit by Mr. Marshall to his mother’s Westchester estate ended with Mrs. de la Renta’s lawyer writing to the Manhattan district attorney’s office, which is investigating whether Mr. Marshall mismanaged his mother’s finances. At that visit, on June 8, Mr. Marshall asked a nurse to show him a tumor developing on his mother’s leg, a lawyer for Mr. Marshall, Kenneth Warner, stated in an affidavit. That request prompted an e-mail from Mrs. de la Renta’s attorney, Paul Saunders, stating that Mr. Marshall’s “behavior endangers Mrs. Astor’s health and welfare,” according to a quote from the e-mail included in Mr. Warner’s filing. Mr. Saunders, according to Mr. Warner, forwarded the e-mail to the top elder abuse prosecutor at the district attorney’s office, Elizabeth Loewy.

Mr. Saunders did not return a phone call seeking comment.

Mr. Marshall’s motive in airing these grievances is to convince the Surrogate’s Court to deny Mrs. de la Renta’s request to be the administrator for Astor’s estate. The sticking point before the court will be how much goes to Mr. Marshall and how much to his mother’s favorite charities and institutions, such as the Metropolitan Museum of Art and the New York Public Library. Early copies of Astor’s will favor the institutions, while later copies favor Mr. Marshall. Noting that Mrs. de la Renta has served on the boards of the Met and the public library, Mr. Warner is requesting for the appointment of an “independent and disinterested person” for the job, according to the filing.