The horse, named Seattle, was one of two police horses patrolling the area of the park near Ingerson Avenue around 6 p.m. about an hour before a 49ers game when a bag flew into Seattle's bridle, San Francisco police spokesman Neville Gittens said.
The horse tried to dislodge the bag by swinging its head back and forth, and the officer riding the horse leaned forward to try to remove the bag, but the horse and officer collided heads and both fell to the ground, according to Gittens.
Seattle quickly sprang up and ran south toward the park's gate B. The horse first ran into a 47-year-old Millbrae man, causing the man to spin around.
Then the horse knocked into 78-year-old Eugene Caldwell, who fell and hit his head, Gittens said.
Caldwell, a resident of Roseville, Calif., suffered life-threatening injuries and was transported to San Francisco General Hospital.
He was pronounced dead at about 1 a.m. today, Gittens said. The Millbrae man and the officer were both treated and released at the scene, according to Gittens.
The Police Department's Mounted Unit has been in existence since 1874 and consists of 10 horses, including Seattle, Gittens said. Seven officers and one sergeant are assigned to the unit.
The officer who was riding Seattle on Friday night is a 28-year-veteran of the Police Department and has been with the Mounted Unit for 10 years, Gittens said.
That officer is also one of the training officers for the Mounted Unit, according to Gittens.
"There's no indication at this point that anything was done wrong," Gittens said. "It was a tragic, unpredictable accident." Seattle has been returned to its stable, but the horse's fate remains unknown, according to Gittens.
