The news emerged in the early-morning hours. Commissioner Bud Selig issued a statement Monday morning.
"Today Major League Baseball mourns the passing of Greg Halman, a member of the Seattle Mariners organization since 2004. Greg reached the Major Leagues in each of the last two seasons, hitting his first career home run on June 15 of this year. Greg proudly represented the Netherlands in the 2009 World Baseball Classic, and he was a participant in MLB International's grassroots clinics in Europe, as recently as earlier this month.
"The loss of a talented 24-year-old young man like Greg, amid such tragic circumstances, is painful for all of us throughout the game. On behalf of Major League Baseball, I send my deepest condolences to the entire Mariners organization and to all those whose lives were touched by Greg."
Michael Weiner, executive director of the Major League Baseball Players Association, issued the following statement:
"We are deeply saddened to learn of the tragic death of Greg Halman. Greg was passionate about the game of baseball and generously gave of himself to share his passion with others in an attempt to help grow the sport's popularity across Europe. He will be sorely missed. ... Our thoughts and prayers go out to Greg's family, his teammates, the Mariners organization and his many friends and fans throughout Europe and America."
Halman, signed by the Mariners in 2004, was their Minor League Player of the Year in 2008 and spent parts of the past two seasons in the big leagues.
"I only knew Greg for a brief time, but I feel lucky that I had the chance to get to know him," Mariners manager Eric Wedge said. "He was a fine young man with a bright future. Greg had a tremendous energy about him, both on and off the field, that I loved. This is just tragic. That's all I can think, that this is so tragic and sad."
The AP reported that police were called to a home in Rotterdam early Monday morning and found Halman bleeding from a stab wound and were unable to revive him, according to Rotterdam police spokeswoman Patricia Wessels.
Wessels said police arrested Halman's 22-year-old brother, who was being questioned.
"It will take some time to figure out what exactly happened," Wessels told The AP in a telephone interview.
"We are shocked and incredibly saddened by the news this morning," Halman's agent, Mike Nicotera, said. "Hopefully in time we will all be able to come to terms with the tragic loss of such a passionate, good-hearted, generous and faithful young man. Our thoughts and prayers are with Greg's family, friends and loved ones. This hurts."
Halman participated in a series of baseball camps for kids in his home country two weeks ago as part of the European Big League Tour, along with a group of other Major League players that included Prince Fielder and Adam Jones.
He was one of nine players born in the Netherlands to have reached the Major Leagues. Orioles pitcher Rick VandenHurk was also born there, as well as pitcher Bert Blyleven, who was inducted into the Hall of Fame last summer.
"Our condolences to Greg Halman's family in Holland," Blyleven said by Twitter. "He played well for us in the WBC in 2009. He had a lot of promise in baseball and life."
Former Major League outfielder Robert Eenhorn is the technical director for the Dutch baseball association.
"The only thing I can say right now is we are deeply shocked," Eenhorn told The AP. "All our thoughts are with his family and how they are going to have to deal with this tremendous loss."
Halman hit .230 in 87 at-bats with two home runs and six RBIs for the Mariners last season. When starting center fielder Michael Saunders struggled early in the year, Halman was called up and played in 35 games before being sent back to Triple-A Tacoma in early August for the rest of the season.
He was on the Mariners' 40-man roster and was regarded as a challenger for a position in left field or as a backup to center fielder Franklin Gutierrez. Free agent closer David Aardsma, a teammate of Halman's the past two years in Seattle, said the young outfielder was a bright presence in the Mariners clubhouse.
"Greg was one of those guys that always came to the ballpark happy, no matter how he was doing," Aardsma said. "He always had a smile on his face and was trying to get better. You could tell he didn't take being there for granted. He put in the work and he was a good guy, a good teammate and somebody who always had your back."
Aardsma is of Dutch ancestry and said Halman always kidded him about needing to learn his native language. Halman himself spoke four languages.
"He'd always call me Dutchy and try to teach me a saying or sentence or word in Dutch," Aardsma said. "Every day I'd mess it up a whole bunch, but I'd try to get it right and then I'd try to surprise him with something I'd learned. He was just a great guy.
"It's hitting me hard. The stories written right now should be how he's battling for a spot on the roster next year and had impressed the brass with where he belongs, not about this. Somebody special got taken from us way too early. I don't know the exact circumstances of what happened, but it's a tragedy for all of us and the Mariners family. It's a sad day."