Mary Kathryn Kostic

Thornton, CO — Mary Kathryn Kostic, 88, of Thornton, CO, formerly of O'Neill, died Feb. 17, 2025 in Thornton, CO.

Services were held Thursday, Feb. 27, 2025 at the Immaculate Heart of Mary Catholic Church in Northglenn, CO. Her funeral Mass is on youtube at https://www.youtube.com/watch?v=1JiVzYQk498.

Burial was in the Broomfield County Commons Cemetery in Broomfield, CO.

Memorials may be made to Saint Mary's, the Immaculate Heart of Mary Parish in Northglenn, CO, or to EWTN in Mary Kay's name, reflecting her commitment to her faith and community.

Horan & McConaty Funeral Service and Cremation in Thornton, CO was in charge of the arrangements.

Born on July 18, 1936, Mary Kay, as she was affectionately known, leaves behind a legacy marked by dedication to her family, career and community.

Mary Kay graduated from Saint Mary's High School and furthered her education at Regis University. 

Her career was notably spent at the Department of Finance and Accounting Service (DFAS), where she retired as an oracle programmer. Her professional life was complemented by a vibrant personal life filled with activities that spoke to her passions.

A devout member of the Immaculate Heart of Mary Catholic Parish, Mary Kay's faith was a cornerstone of her existence. She was deeply involved in her community and cherished the friendships she made through her church.

Her hobbies included gardening, where she took particular pride in her tulips and roses, and playing softball, where she was a spirited member of her work team. Mary Kay was also an enthusiastic genealogist, tracing her family roots back to Ireland, an endeavor that led her to become a recognized Daughter of the American Revolution.

Her life was a testament to her strong will, loving heart and unwavering faith, and she will be deeply missed by all who knew her.

Mary Kay is survived by her youngest sister Elizabeth Crow, and her son Bill. 

She was preceded in death by her beloved husband Bill Kostic in 2020, her brother Gene Turner, two sisters Donna Reising and Janice Lemek and two nephews Tom and Doug Reising.