A blue Ford Focus rental car erupted into a ball of flames with 25-year-old Alex Martin inside it, after a US Border Patrol agent broke the car’s passenger side window and shot a Taser into the cab, igniting gas fumes inside.

The blast was so strong it blew agents backwards, leaving them to regroup before they moved their cars away from the burning small car without attempting to help Martin.

The scene is part of a disturbing video released last week as discovery in a lawsuit against the agents involved in the March 2012 incident. Martin’s family filed the suit after he burned to death in the blaze.

“For some reason, even though each of those cars had a fire extinguisher readily within reach, none of them used their fire extinguishers – or tried to used their fire extinguishers, or tried to help Alex – who was burning to death inside this car,” said Gene Iredale, the attorney for Martin’s family.

“You’ll see in this video they just walk away, and consult with each other.”

The fire was so intense that Martin’s remains were 50lbs lighter than the 185lbs he was believed to have weighed when he left his home in Texas, his attorney said.

The disturbing video comes after years of increased scrutiny of the US Border Patrol, which is part of the Department of Homeland Security. The agency has been criticized for using excessive force and having poor accountability.

The Border Patrol said in a statement that it was aware of the lawsuit, but couldn’t comment because of the pending litigation. It referred questions to the US attorney’s office.

Attorneys for the government argued this month that the lawsuit should be dismissed because it involves no clear constitutional violations. In a motion, US attorneys in San Diego argued that “the use of force by the agents was justified and reasonable” and that there was “insufficient evidence of any wrongful conduct to support those claims”.

The events that led agents to break Martin’s passenger side window in order to gain access to his car remain in dispute.

Though Alex and his mother, Karen Martin, planned a trip to San Diego, they canceled the plans at the last minute. Nevertheless, Alex Martin rented a car from Dallas-Fort Worth airport. The contract was for two days, despite the fact that it takes 19 hours to drive between the two cities. Government attorneys have argued that Martin’s destination was never established, though Iredale said he believes Martin was attempting to drive to San Diego.

Martin was not supposed to be driving the Focus in the first place. As part of a DUI case he was required to drive vehicles equipped with a breathalyzer. He had evaded police during that arrest as well, and was found with a gun when he was taken into custody.

The government also pointed to bizarre notes found in Martin’s possession after the fire. Some included phrases about “The Mystical Destiny of the Aryan Man” and “Hitler/Nazi = (Homosexuality)”.

Agents first made contact with Martin around midnight. Agent Alex Fishman claims Martin was seen driving the wrong way on Interstate 8, but he wasn’t pulled over until he was stopped at a cul de sac. (Iredale disputes this claim, saying it is unclear Martin and the wrong-way driver are the same person.) Martin may have been trying to work out where he was – a neighbor said Martin had asked for directions, Iredale said.

Agents approached Martin in an unmarked car, in plain clothes and with lights on. Martin fled, driving for about three minutes at speeds up to 75mph, his attorney said. Customs agents deployed spike strips as Martin drove through a checkpoint on Old Highway 80, deflating the Focus tires, and stopping the car a little more than a quarter-mile down the road.

There is no audio track to the video, but Martin’s family attorney said plain-clothes agents then gave conflicting directions – including “hands up”! “Get out of the car!” and “Roll down the window!”

“He couldn’t comply with any one command without violating or contradicting the other three,” Iredale said.

Also in dispute is whether agents smelled gas fumes, something which would have been a clear indication against using a Taser, which are known to ignite flammable gases.

Whether the case goes to trial will be decided by a federal judge in the southern district of California. The judge has no deadline on deciding whether to accept the motion for summary judgment from the government, or to allow the case to go before a jury, as Iredale and Martin’s family hope.