(CNN) -- It's an iconic piece of video.
For more than three minutes, a mob of enraged men toss Moammar Gadhafi around like a broken mannequin. His body and face bloody, his black bushy hair a crazy mess, the 69-year-old Libyan leader is pummeled. His shirt is ripped open to reveal a pudgy belly.
The cell phone camera then focuses on a gulf of red spreading across Gadhafi's backside as someone stabs him in the rear with a bayonet.
Later, a young man holds a golden pistol triumphantly in the air as he's cheered by the mob in Sirte, Libya.
It didn't take long before the video was uploaded to the Internet, where the world watched the violent end to Libya's eight-month uprising in 2011 -- and to Gadhafi's life.
To critics of the long-ruling dictator, it appeared to be a fitting conclusion. But human rights investigators now say there's much more to what happened on October 20 last year than rebels acting in the heat of the moment.
Human Rights Watch says the militiamen who ravaged Gadhafi also captured, tortured and killed dozens of his loyalists following his death, violating international war crimes laws.
That assertion is laid out in a 50-page report released by HRW this week. The rights group based its findings on witness accounts and amateur videos shot with cell phones.
In its report, HRW lambastes Libya's current transitional government, saying it has taken no serious steps in investigating or prosecuting anti-Gadhafi militias. It also says its findings do not match Libya's assertion that Gadhafi was killed in the crossfire, and not after his capture.
HRW called on Libya's leaders to honor their pledge formally and investigate Gadhafi's death.
CNN has reached out to Libyan authorities for comment on the Human Rights Watch report, but has not received a response.
If Libya is going to truly rid itself of violence and extremists -- a timely demand considering last month's fatal U.S. consulate attack -- justice, the group believes, must be meted out on all sides.
Gadhafi and crew run
In February 2011, protesters took to the streets in Libya demanding peacefully that Gadhafi step down. His 42 years of hardline rule had to end, they said.
A man who rarely embraced reality, Gadhafi retorted, "All my people...love me."
As rallies continued, Gadhafi responded by ordering his forces to fire into the crowds. The movement descended into a violent uprising that dragged on for months.
By March, the opposition gained a foothold in the city of Benghazi. In response, Gadhafi's forces closed in on the city.
At the United Nations, the Security Council passed a resolution imposing a no-fly zone over Libya and authorized the use of "all necessary measures" -- except an occupation -- to protect civilians from the violence raging in their country.
In August, as Tripoli looked ever more fragile, Gadhafi, his crew and his sons jumped into cars and sped off in various directions.
Khamis Gadhafi, active in his father's regime, was killed in a NATO airstrike as he tried to skip town.
Another son, Saif al-Islam, managed to make his way to the Misrata suburb of Bani Walid, surrounded by desert.
Al-Islam later told Human Rights Watch that a NATO airstrike had left him mildly wounded. He was captured in November near Libya's border.
National security adviser Mutassim Gadhafi, another son, made it safely to Sirte, his father's hometown.
That's also where the dictator and his crew headed.
Senior security adviser Mansour Dhao was in tow, he told Human Rights Watch, as well as Gadhafi's personal guard, driver and a bunch of other bodyguards.
Libya's intelligence chief was there, but only briefly, because he was dispatched hundreds of miles to the south of Sirte. His job? He had to tell Khamis' mother that her son was dead.
From luxury to squatting
For some time, Gadhafi and his inner circle stayed in the middle of the city. But as the fighting intensified, they began moving from empty house to empty house, eating the food left in the cupboards, Dhao said.
The homes they sought shelter in had already been looted. As the weeks wore on, food was sparse. The medicine they had was running out. It was getting tougher to find water.
This group, who once dined in luxury, was subsisting on pasta and rice.
"Living (was) very hard... we didn't even have bread," Dhao recounted.
Gadhafi spent most of his time reading the Quran and praying.
"His communications with the world was cut off... no television, nothing," Dhao said. "No news. Maybe we could use the (satellite phone) and get some news from al-Rai, Russia Today, BBC or France 24. I mean, (we) could call people who watch those channels.
"We had no duties," he said. "We were just between sleeping and being awake."
The militias hunting Gadhafi were getting closer. And the dictator was getting moodier.
"(He was) becoming more and more angry," Dhao said. "Mostly he was angry about the lack of electricity, communications, and television, his inability to communicate with the outside world."
The men would sit with Gadhafi and try to calm him down.
"Why is there no electricity?" he screamed at them. "Why is there no water?"
A doomed escape
By mid-October, Mutassim, one of the two surviving sons, decided enough was enough. He told the group in Sirte to meet at an ad-hoc clinic. They were going to try to escape.
The plan was to break out around 3:30 or 4 a.m.
But it took until about 8 a.m. to load the supplies and the men who were wounded. By that time, anti-Gadhafi militia fighters had returned to their fighting positions.
Odds were stacked against the convoy, not least of all because it was unwieldy, including some 250 people.
When it set out, it came under heavy attack. It swerved and snaked onto dirt roads.
A missile struck so close to the convoy that airbags in some of the vehicles inflated, Dhao said.
Disoriented and out of options, Gadhafi's men drove right into a militia base.
As NATO jets flew overhead, the vehicles were trapped. Munitions inside the convoy were triggered by the firepower all around. Explosions shook Gadhafi's crew from the convoy and they ran for their lives.
Younis Abu Bakr Younis, the son of Gadhafi's defense minister, was among several who ran to a villa and took cover.
When he got there, he saw Gadhafi hiding, wearing a helmet and bulletproof vest. The dictator had a handgun in his pocket and was carrying an automatic weapon, Younis and another witness told Human Rights Watch.
Shots picked away at the concrete.
Mutassim Gadhafi was injured but he still called the shots.
He ordered the men to make a run for it, and motioned toward a drainage pipe near a main road several hundred feet away.
Mutassim turned to his father.
"I will try and find you a way out of here," he promised.
Once they made it to the pipe, fighters ran toward the group. Gadhafi's guard threw a grenade at them.
It bounced off the concrete and back at them.
The mob descends
Shrapnel sliced Gadhafi. Dhao saw that the leader's head was bleeding. But he was more concerned with his father, who was also with the group. He'd fallen to the ground.
"I ran towards my father, but he didn't answer when I asked him if he was okay," Dhao told Human Rights Watch.
Younis, the son of Gadhafi's defense minister, was fatally injured.
A guard was dead.
Exposed, the group was overrun by militia fighters.
The 3-minute, 38-second cell phone clip that seems to show the last moments of Moammar Gadhafi's life is choppy. Whoever was filming moves the camera around dizzily in the chaos. But the audio is clear.
The mob shouts "Allahu Akbar!" or "God is the greatest!"
They chant "Misrata," the name of the town where hatred of Gadhafi burned most intensely during the uprising, primarily because his army had shelled it nonstop for two months in the spring.
To understand precisely what shelling means here, imagine the kind of Fourth of July firework that shoots up to the sky in a single rocket and then bursts into a thousand pieces in the sky.
If you were on the ground in Misrata, it was like that, only in reverse, a thousand tiny death pellets careening in all directions at speeds impossible to run from.
Scores of innocent people were killed there, and even if they survived the shelling, there wasn't much hope. It was next to impossible to get medical aid, food and other supplies there.
It was the militias of Misrata that brutalized Gadhafi loyalists the worst, the rights group says.
The group also alleges it has evidence that indicates opposition militias took Mutassim from Sirte to Misrata and killed him, and it has cell phone video taken by opposition fighters showing captured convoy members being abused, the group said in its report.
Human Rights Watch matched morgue pictures with video of men executed together in a hotel.
HRW had investigators inside Libya the day Gadhafi died. The team documented more than 100 bodies and wrote in the Wednesday report that the bodies lingered for a while but were later buried by volunteers. The rights group alleges that no Libyan investigators have attempted to document how many people died, who killed them and how.
The problem, Human Rights Watch says, is twofold. First, those militias from Misrata are still quite active. Today, they are preventing about 30,000 people from returning to their homes in the area, for example.
Second, the country's transitional government perceives them as undermining governmental authority, the rights group said.
Suspicion -- rather than order and forgiveness -- continues to grip Libya, the rights group suggests, and justice is being ignored.