The Phoenix, Baltimore County, resident had just completed two dressage competitions in Leesburg when he was stricken.
Born in Baltimore and raised in Carney, Mr. Obrigkeit was a 1974 graduate of Parkville High School.
Mr. Obrigkeit, who began riding at 14 when he purchased his first horse, was a 1975 graduate of Meredith Manor, an equestrian school in Waverly, W.Va., where he had earned a master's certificate.
"Bill was a talented and exceptional dressage rider," said his companion of 14 years, Keith A. Merkey of Phoenix, who is a trainer with the Maryland State Department of Education.
Mr. Obrigkeit owned two warmbloods used in dressage competitions that he had purchased in Germany.
He was a member of the U.S. Dressage Association and a founding member of the Maryland Dressage Association.
In his professional life, Mr. Obrigkeit had worked for 33 years for Bank of America, spending many years in the bank's Light Street office.
At the time of his death, he was assistant vice president and assistant manager of the bank's Hunt Valley branch.
"His horses were his main interest, but he loved his Welsh corgis," said his mother, Carolyn Obrigkeit of Phoenix.
Mr. Obrigkeit was a member of St. Mark's Lutheran Church on St. Paul Street in Baltimore.
Services were Wednesday at Peaceful Alternatives and Cremation Center in Timonium.
Also surviving are his father, Frederick "Fritz" Obrigkeit of Phoenix; a brother, Frederick Obrigkeit Jr. of Phoenix; a sister, Karen Beckley of Phoenix; and several nieces and nephews.