Villalona turned himself in to local authorities Sunday afternoon.
"The Giants were disappointed to learn that there was an incident in the Dominican Republic last night in which an individual was killed and one of our Minor League prospects, Angel Villalona, may have been involved," the team said in a statement released Sunday. "We will monitor the situation closely and trust that the judicial process in the Dominican Republic will resolve the matter promptly and fairly."
"We know there was an incident and that there is one person dead, but we don't have the details of the case," said Frank Micheli, president of the Azucareros del Este team in the Dominican Winter League. Villalona is affiliated with the Azucareros for winter baseball.
According to the AP, Villalona will appear in court Monday and could face up to 20 years in prison if found guilty.
"It's a shock, obviously," said Giants catching prospect Buster Posey, who began the season with Villalona at high-Class A San Jose. "But I don't want to comment too much on something I don't know about."
Posey raved about Villalona's personality. "I loved him," Posey said. "I enjoyed being around him."
Right-hander Waldis Joaquin, a fellow Dominican who played with Villalona at low-Class A Augusta last season, didn't address his former teammate's case specifically. But Joaquin pointed out that in his country, people occasionally shoot first and answer questions later if they're being hassled by a group.
"Maybe if you have five people in one fight, you don't want to leave, and if you have a gun, you [fire it]," Joaquin said.
Villalona, ranked No. 48 in MLB.com's preseason Top 50 Prospects list, made headlines in 2006 after receiving a $2.1 million signing bonus with the Giants as a 16-year-old. The deal represented the Giants' first and most noticeable move in its renewed effort to obtain talented players internationally.
The Giants brought Villalona along slowly, due to his youth and inexperience and also to allow him to gain an understanding of American culture gradually. After playing on the rookie-ball level in 2007, he rose last year to Augusta, where he hit .263 in 123 games with 29 doubles and 17 home runs. Former Giants outfielder and manager Felipe Alou, now a special assistant to general manager Brian Sabean, likened Villalona to Andres Galarraga, the five-time All-Star first baseman who hit 399 home runs.
Villalona, who signed as a third baseman but was moved to first base, impressed enough other observers to be selected for the World Team in the 2008 XM All-Star Futures Game at Yankee Stadium. Before this season, Baseball America rated him as the Giants' third-best prospect behind left-hander Madison Bumgarner and Posey.
Villalona hit .267 with nine home runs and 42 RBIs in 74 games with San Jose in 2009 before being shut down in early July with a quadriceps injury.
Villalona was expected to return to the United States soon to begin participating in the Giants' instructional league camp in Arizona.