At least three people were killed in an attack on emerald dealer Pedro Nel Rincon, who was wounded by shrapnel from a grenade, Colombian media reported.
The attack occurred on Saturday at the sports complex in Pauna, a city in the central province of Boyaca, where Rincon was hosting the Peasants Festival.
An unidentified individual threw a grenade into the area where Rincon, his son and several other people were.
"Pedro was wounded, not badly, but one son is in pretty delicate condition," Engativa Bishop Hector Gutierrez Pabon told Noticias Uno.
An adult and an 18-month-old baby were pronounced dead at the scene, while a third person died a few hours later at the hospital in Chiquinquira.
Rincon's bodyguards engaged the assailants in a shootout after the grenade attack, eyewitnesses said.
Police are working to determine the motive for the attack and trying to identify the assailants.
Rincon has been identified as an enemy of Victor Carranza, who died in April and was known as the "emerald czar."
Carranza told officials before his death that Rincon planned attacks against him and other individuals involved in the emerald trade.
Former paramilitary commanders Freddy Rendon and Julio Sierra told authorities that Rincon financed the entry of the United Self-Defense Forces of Colombia, or AUC, militia federation into Boyaca in 2000.
The majority of the defunct AUC's leaders were extradited to the United States to face trial on drug charges.
The militia group was made up of numerous rural defense cooperatives formed more than 20 years ago to battle leftist rebels.
Many of the militias, however, degenerated into death squads and carried out massacres of peasants suspected of having rebel sympathies, along with slayings of journalists and union members accused of favoring the leftist insurgents.
The AUC, accused of committing numerous human rights violations, demobilized more than 31,000 of its fighters between the end of 2003 and mid-2006 as part of the peace process with former President Alvaro Uribe's administration. EFE