A motorist who shot dead two environmental protesters blocking a road in Panama on Tuesday is a retired American lawyer, it has been revealed.

Kenneth Darlington, 77, appeared before a judge in the town of La Espiga on Wednesday afternoon, and after a two-hour hearing was remanded in custody.

According to local media, the Panamanian-born US citizen - who was seen in both video and pictures shooting dead two teachers blocking a road on a highway - has a previous conviction for illegal possession of a firearm.

It is understood he declared 'this ends here' before walking up to the road block on a section of the Pan-American Highway in the Chame district and getting into a heated argument with a group of men that included the two victims.

In front of a large number of photographers and television crews there to film the protest, he then gunned down the two men.

Eliécer Plicett, a lawyer for the two victims, said Darlington was being charged with murder and illegal possession of a gun, TVN Noticias reported. However, local media has reported he could avoid jail time because of his age.