BOGOTA, Colombia (CNN) -- A Colombian former hostage -- released by Marxist guerrillas after nearly seven years in captivity -- said the rebels who held him and 11 colleagues killed the others in cold blood, an act he called "a war crime."
Former regional legislator Sigifredo Lopez arrives Thursday in Cali, Colombia, after FARC rebels freed him.
Speaking upon his arrival in Cali hours after his release Thursday, former regional legislator Sigifredo Lopez said he never saw what happened the day his fellow lawmakers died because he had been separated from them as punishment for supposedly being a troublemaker.
Rebels of the Revolutionary Armed Forces of Colombia, better known as FARC, had taken him to another part of the campground, chained him to a tree and built a small wall made from palm fronds so he couldn't communicate with the other captives.
"I suffered the unmentionable," Lopez said. "My colleagues never should have been assassinated as they were assassinated by the FARC the 18th of June at 11:30 in the morning in the year 2007." Watch Lopez's reunion with his family after nearly seven years in captivity »
The FARC said the captives died in cross-fire during a military rescue mission. The Colombian army blamed the rebels.
When the bodies were recovered three months later, autopsies showed most had been shot multiple times in the back.
Lopez was the sole survivor.
At a Thursday night news conference, he described what he heard that day and what a rebel later told him happened.
He had just finished lunch, he said, when he heard two shots, followed immediately by another two shots. He threw himself on the ground, thinking it was a rescue effort by the Colombian military.
His only thoughts, Lopez said, were, "My God. My God. Save me. I commend my little sons and my family to you."
A few minutes later, Lopez said, sustained bursts of gunfire started. He heard yelling, and then he heard a voice he recognized as a rebel leader say, "Don't let them go. Don't let them go." After a while, the gunfire stopped. Then silence.
Later, a rebel told him Colombian soldiers had come across the camp and a guerrilla commander gave the order, "Kill them [the hostages] and let's go."
"Why did they kill them?" Lopez asked at the news conference. "Because of something called paranoia. For physical cowardice. This was an assassination. This is what is called a war crime."
Lopez, who was abducted April 11, 2002, is the sixth hostage released by the rebels in a week. But few of the hundreds of kidnappings attributed to the FARC were as dramatic as the one in which Lopez and the 11 other lawmakers were snatched.
A videotape made by the FARC that day in 2002 and released in 2006 shows the first minutes of the bold abduction. Watch the footage of the dramatic kidnapping »
The rebels had been training for months at a FARC camp, practicing in army and police uniforms in a mock-up of the regional parliament made with plastic tarps and sticks.
A rebel camera was rolling as the 20-strong commando group drove a bus to Cali, Colombia's third-largest city. Salsa music was blaring.
They were posing as government soldiers. Motorcycle outriders cleared the way.
Once they reached the parliament building, they faked a bomb alert.
The bus pulled out in front of the building and the video shows people running from the perceived threat.
On the video, an unseen rebel is heard to say, "For the deputies, we have a special vehicle."
Twelve congressmen took their seats, believing the military was shepherding them to safety. Minutes passed, and one politician asked where they were headed.
A few minutes later, the muffled reply can be heard: "Ladies and gentlemen. We are the FARC."
Back in the mountains, the hostages were herded aboard a truck. Guerrillas waved and hugged as they celebrated their audacious mission.
In 2003, Lopez and some of the other hostages appeared in a proof-of-life video. One of his colleagues simply wrote, "Until when?" on his hand and held it up to the camera.
Another, Jairo Hoyos, sent a prophetic plea to the president: "Mister President. Those who are about to die salute you."
Colombia has said the rebels are still holding about 700 captives.
The FARC unilaterally released six of them in the past week.
On Tuesday, Alan Jara, the former governor of Colombia's Meta state, arrived at the airport in Villavicencio, southeast of Bogota.
Four other hostages -- three police officers and a soldier -- were released over the weekend.
Colombian Sen. Piedad Cordoba has brokered the releases with the help of the the International Committee of the Red Cross and a group called Colombians for Peace. Brazil also helped, providing the aircraft used in the releases.
The FARC, the largest and oldest guerrilla group in Colombia, announced the releases December 21 and designated Cordoba as the coordinator.
The guerrillas had wanted to swap the hostages for about 500 colleagues jailed in Colombia and the United States, but the government steadfastly has refused.
Some analysts see the hostage release as a first step toward an eventual peace accord. Others suggest it's another sign that government military gains, combined with a tough right-wing political line, are gradually beating the FARC into submission.
Security analysts said FARC has about 9,000 to 12,000 armed guerillas and several thousand supporters, mostly in rural areas.
The guerrilla group operates mostly in Colombia but has carried out extortion, kidnappings and other activities in Venezuela, Panama and Ecuador, analysts said.
CNN's Karl Penhaul contributed to this report.