The November 23 massacre in the southern Philippine province of Maguindanao was the country's worst single incident of politically-related violence, leaving at least 57 people dead.
The killings are believed to have been masterminded by a leading member of a powerful local clan, Andal Ampatuan Jr, also known as Datu Unsay, in an attack on the family of a political rival.
More than 20 accompanying journalists and some passers-by were also killed in what investigators say was an attempt by the attackers to cover their tracks.
Ampatuan Jr is now being held in a Manila jail accused of multiple counts of murder, although his trial was recently suspended indefinitely, pending decisions on motions filed by his lawyers.
Speaking to Al Jazeera, Jesse admitted he had taken part in the November killings, but said that as an employee of Ampatuan Jr's cousin, he had to either kill or be killed.
And he said the attack was carried out not on Ampatuan Jr's orders, but on the orders of his father, the clan patriarch and former governor of the province.
"I was there when they met a week prior and talked about the killings," he said.
"Unsay only does what he is told by Andal Sr… I followed orders too… I fired shots, I don't know how many I hit … if I hadn't - well, we know what Unsay is like."
Now in hiding and using an assumed name, Jesse is awaiting a decision from Philippine authorities on his plea for witness protection in return for his testimony.
In the meantime, he says, Ampatuan Jr has placed a $45,000 bounty on his head.
The Ampatuan clan has fiercely denied any involvement in the massacre.
Ampatuan Sr has controlled Maguindanao province for most of the past decade and had been grooming his son to take his place as governor in national elections scheduled for May.
|The trial of Ampatuan Jr, also known as Datu Unsay, has been suspended [Reuters]
The family also had close political ties to Gloria Arroyo, the Philippine president who critics say had allowed the Ampatuans to build up a powerful militia in return for delivering votes.
Marga Ortigas, Al Jazeera's Manila correspondent, says the investigation into the massacre has been seen as a test not only of the Philippine judiciary but of the strength of the country's democracy as a whole.
While dozens of other clan members have been charged in relation to the killings, only one man – Ampatuan Jr – has so far been brought to court.
With his trial now suspended, many Filipinos are sceptical that the perpetrators of the massacre will ever be brought to justice.
Court authorities have rejected accusations of political pressure and say they are doing the best they can.
In any case, Jesse told Al Jazeera, inside or outside of jail, the Ampatuan clan has a long reach.
"Unsay has been telling his men to be patient, that he'll get out," he said.
"And when he does, he will punish anyone who turned against them."