Phillies players and personnel were informed of the news by club president David Montgomery in a somber pregame meeting.
In a hallway outside the visiting clubhouse, Montgomery fought back tears as he addressed a large group of reporters who had assembled after hearing Kalas had been stricken.
"Sadly, I must confirm that we lost Harry. We lost our voice today. Harry loved our game and made a tremendous contribution to our sport, and certainly to our organization," Montgomery said.
The Phillies had been scheduled to visit the White House today, but Montgomery said the visit had been postponed indefinitely.
The Phillies won the game, 9-8, and dedicated the win to Kalas.
"He's our angel now," outfielder Shane Victorino said after the game. "I'm sure he was calling the game from upstairs."
Montgomery described the players as stunned after receiving the news.
"They treated this as news of a tragedy that happened to a teammate," he said. "Harry was like a teammate to them."
The Nationals organization, hosting its home opener, honored Kalas' memory with a moment of silence before the first pitch.
"He was the heart and soul of the Phillies organization," the stadium public-address announcer told the crowd.
As Kalas' picture flashed on the video board above right field in the hushed stadium, a fan shouted: "We love you, Harry."
Chris Wheeler, a longtime broadcast partner of Kalas', wondered if the Phillies could have played if the game weren't on the road.
"It would have been hard to play if this had been a home game," Wheeler said.
The team did not say how the broadcast team will be affected by Kalas' absence.
Wheeler recalled that he joined the Phillies in 1971, the same year as Kalas.
"He helped me when I went into the broadcast booth," Wheeler said. "He taught me a lot about how to be a professional and do the job. We spent a lot of time together."
Wheeler recalled joining Blue Bell Country Club in 1994. His first foursome included Kalas, Richie Ashburn and Kalas' son, Todd. Harry Kalas and Ashburn were a broadcast tandem beloved by Phillies fans. Ashburn died after calling a game in Sept. 1997 at Shea Stadium.
"Harry was a great friend on and off the field for many years," Wheeler said.
Known for his classic "Outta here!" home-run call, Kalas was the recipient of the Ford C. Frick Award and was honored by the Baseball Hall of Fame at its 2002 induction ceremony.
Despite his celebrity, he was always approachable and down to earth.
"It was a real inspiration to watch the way he connected with our fans," said Scott Franzke, who joined the broadcast crew in 2006. "He never said no to an autograph or a photo with somebody. He never turned down being somebody's outgoing voice-mail message when they asked him to. And he didn't have to do any of that at this stage. He was already Harry the K.
"It was a real lesson to remember why we do what we do - and it's for the fans. We love the game. We make a very good living at it. It's a fun job to do. But we do it for the fans."
Franzke fought back tears.
"The players come and go, but 'Outta here' lasts forever," he said. "Harry was always first class in the way he treated people. He was a genuinely nice guy."
Broadcaster Larry Andersen recalled his friendship with Kalas, which started during his playing days. Kalas was always one of the boys, sitting on the back of charter airplane flights, sharing a cold one with the players.
"No matter who the player was, there was always a silver lining," Andersen said. "He never got on a player. He never bad-mouthed a player. He always looked for the positives, no matter who it was. The players appreciated that. He found the good in everybody and especially the players. He loved the players. He loved being around them."
Andersen said Kalas did not ride in the back of the plane en route to Denver and then to Washington on this road trip.
"It was like, 'It's not right,' " Andersen said. "It was almost like an omen. He was always in the back row. He wasn't feeling well. You could see it. You could tell."
Kalas had heart surgery - stents were put in - in February, but was able to make it to spring training by mid-March. However, he appeared thinner than normal, even weak.
After he collapsed yesterday, Kalas was found on the floor of the broadcast booth by Rob Brooks, the team's director of broadcasting. Emergency medical technicians treated Kalas on the scene and took him to George Washington University Hospital, where he was pronounced dead at 1:20 p.m. Cause of death was not immediately known.
Andersen said his favorite memory of Kalas came after the Phillies won the NL East title in Pittsburgh in 1993.
"Him leading us in 'High Hopes,' " said Andersen, crying. "I don't ever want to hear that song again."
Bob Boone, a catcher during the Phillies' glory years decades ago and now an executive in the Washington front office, said he was saddened by Kalas' death.
"Harry was part of that whole Phillies growing-up period in the 1970s," Boone said. "He was one of us when we won the World Series in 1980. To lose him is shocking."
So how will the Phillies handle the absence of Harry Kalas in the broadcast booth?
The team had no announcement yesterday on any restructuring of the broadcast team of Chris Wheeler, Larry Andersen, Scott Franzke, Gary Matthews, Tom McCarthy and Jim Jackson, the pregame and postgame host.
For yesterday's game, McCarthy filled in for the duties that Kalas would normally perform.
Watch videos of Harry Kalas calling the last outs of the Phillies' 2008 World Series and National League East victories, and singing "High Hopes."
Listen to announcers at yesterday's Phillies/Nationals game mark Kalas' passing.
See photo galleries of Kalas' career in Philadelphia.
Sign a guestbook.
Read coverage of Kalas from The Inquirer's archives.
Find all coverage at www.philly.com.
Harry Kalas' death touches all all who knew him. A1.
When it came to the Phillies, he was The Voice. Bill Lyon, A1.
The longtime Phillies broadcaster made us all fans of the game. Gonzo, E6.
There was a special bond between Kalas and Rich Ashburn, and the fans loved it. E6.
At NFL Films, Kalas was far more than a baseball voice. E6.
Contact staff writer Jim Salisbury at 215-854-4983 or email@example.com.