Bloomberg offers some clues, as well as a few other tidbits:

Colombia Pays Rebel in Boss's Murder as FARC Weakens
March 14 — Colombian President Alvaro Uribe ordered a reward paid to a former rebel who killed his commander, setting aside moral concerns as the government tries to provoke betrayals among the weakening insurgents.

Pedro Pablo Montoya, known as Rojas, will get part of a $2.7 million reward for slaying Ivan Rios, a top commander in the Revolutionary Armed Forces of Colombia. Rojas, Rios' security chief, turned on his boss while troops closed in, then cut off the dead man's hand as evidence and surrendered with Rios' computer. Three other informants will share the reward.

"We pay for information and other types of collaboration," Defense Minister Juan Manuel Santos told reporters today in Bogota. "What we have in that computer is very valuable information."

[...]

Rebel Succession

On March 12, troops killed a guerrilla known by the alias Genaro, second in command of one of the FARC's most active and bloody columns known as the Teofilo Forero Mobile Column.

Santos said information provided by Rojas has enabled the army to intensify operations against two guerrilla fronts in Antioquia, Caldas and Choco provinces.

The FARC, financed by kidnapping and drug trafficking, is led by 77-year-old founder Marulanda, who may be in Venezuela and suffering from cancer. Disease and combat casualties have cut the FARC's ranks to about 8,000 fighters from more than 17,000 at its peak, according to government figures.