( CNN ) -- Colombia 's main leftist rebel group shot and killed four hostages held for more than a decade , President Juan Manuel Santos said Saturday , vowing to fight the rebels with everything in reach . A fifth hostage , a policeman , was found alive , Defense Minister Juan Carlos Pinzon told reporters . `` This is yet another example of how brutal and cruel the FARC is . ... When faced with security forces , they ( the rebels ) had no qualms about killing them in cold blood , '' Santos said . The Revolutionary Armed Forces of Colombia , known as FARC , has been at war with the Colombian government since the 1960s . While severely weakened in recent years , the guerrilla group has continued to carry out kidnappings and attack security forces . Chains were found near the bodies of the four hostages , who were kidnapped `` more than 12 or 13 years '' ago , Santos said . The president called the killings a `` crime against humanity '' and swore their only effect would be to make police and soldiers more determined to fight `` with everything in reach . '' The bodies of the four men , all of whom were security force members , were found in the morning , according to Pinzon . They were executed in the southern region of Caqueta , where the military was conducting operations against the rebel group , he said . Three of the hostages were shot in the head , while the fourth was shot in the back , the defense minister said . The fifth hostage , identified as Luis Alberto Erazo , had been held for roughly 12 years , Pinzon said . He reportedly ran from the rebel camp at the start of a firefight between rebels and Colombian troops . His condition is `` acceptable , '' Pinzon said . Earlier this month , a military operation killed then-FARC leader Alfonso Cano . Following his death , the FARC released a statement in which its leaders said they would not end their guerrilla struggle .
NEW : A fifth hostage is still alive , Colombia 's defense minister says . Colombia : President Juan Manuel Santos calls the attack a ` ` crime against humanity '' The hostages were reportedly shot in the head and the back . A military operation earlier this month killed former FARC leader Alfonso Cano .