DENVER -- A 27-year-old man who fell about 20 feet and struck his head on concrete during the seventh inning of a Colorado Rockies game has been declared dead, authorities said Thursday.

Witnesses told police that the man had been trying to slide down a staircase railing at Coors Field and lost his balance during Tuesday afternoon's game between the Rockies and the Arizona Diamondbacks, Denver police spokesman Sonny Jackson said.

The Denver coroner's office identified the man Thursday as Robert Seamans of Pueblo, Colo. The father of Seamans' girlfriend, Larry Elliott, told The Denver Post that Seamans was declared brain dead on Wednesday, about 12 hours after the incident. A transplant team was called in to harvest his organs, Elliott said.

"You definitely don't want somebody's experience at the ballpark to be something like that," Rockies first baseman Jason Giambi said before heading to batting practice before Thursday's game against Arizona. "It's supposed to be uplifting and an enjoyment for the fans. That's a terrible thing to hear."

Seamans worked as a waiter at Cactus Flower Mexican Restaurant in Pueblo for at least the past four years, restaurant general manager Kim Harding said. She described Seamans as playful and a favorite of customers who often asked for him by name.

Seamans had plans to attend the April 3 game between the Rockies and Diamondbacks, but that game was postponed because of rain.

Harding said Seamans was very excited about attending Tuesday's makeup game, the first of a doubleheader.

"He was like a kid on Christmas," she said. "I'm not sure if this was his first baseball game."

Seamans' family declined to comment when reached by telephone at their Pueblo home on Thursday.

The Rockies said in a statement Thursday that they were deeply saddened to learn of Seamans' death.

"Our thoughts and prayers remain with the family and friends of this young man as we all grieve for his loss," the club said.

Denver's chief deputy coroner, Michelle Weiss-Samaras, said an autopsy was planned Thursday, but results weren't immediately available. Toxicology tests could take weeks, she said.