Shannan Maria Gilbert was born to Mari and Floyd Gilbert and was one of several daughters raised by her mother, Mari Gilbert. Shannan had three sisters

• Sherre Gilbert
• Sarra Gilbert
• Stevie Smith

Mari Gilbert

• Mother of Shannan
• Mari Gilbert was born on June 22, 1964, in Lancaster, Pennsylvania
• Mother: June Rose C. Gran, a deeply religious woman known for frequently changing churches
• Father: John W. Cox Sr., a brick maker who struggled with heavy weekend drinking.
• Mari married Floyd Gilbert
• Floyd struggled with schizophrenia and cocaine addiction
• Together they had three daughters
• Became one of the most determined and outspoken advocates for justice after Shannan disappeared in 2010
• Refused to accept early claims that Shannan died accidentally
• Pressured law enforcement, held rallies, engaged media, and fought to keep attention on the case
• Retained attorney John Ray to investigate independently and to challenge official conclusions regarding Shannan’s death
• Filed civil action related to the investigation and circumstances surrounding the Oak Beach community

Mari Gilbert is widely credited with preventing Shannan’s case from being dismissed and with helping keep national attention focused on the Long Island Serial Killer investigation.

Sherre and Stevie

• Both sisters have spoken publicly about Shannan’s disappearance
• Continued Mari’s efforts to keep the case active
• Participated in public advocacy, media interviews, and court hearings
• Have repeatedly pushed for answers and accountability

Sarra Gilbert

• Struggled with severe mental illness
• On July 23, 2016, Sarra tragically killed her mother, Mari Gilbert, inside Sarra’s apartment
• Sarra was convicted and sentenced to prison
• This devastating event compounded the trauma the family had already endured because of Shannan’s disappearance and death

Family Role in the Investigation

• The Gilbert family consistently argued that Shannan was not simply lost or accidentally drowned
• They challenged the Suffolk County determination that her death was not homicidal
• They advocated for continued investigation and greater transparency
• Attorney John Ray frequently represented their position publicly and in court
• The family repeatedly emphasized that Shannan’s case should be viewed within the broader Gilgo Beach investigation

Legacy

• Shannan’s family transformed their grief into forceful advocacy. Their persistence played a significant role in keeping the case active, increasing scrutiny on police leadership, and maintaining sustained public attention on the Gilgo Beach victims. Despite profound personal tragedy, the family has continued to push for truth, accountability, and recognition of Shannan as a central figure in the investigation.