Two law enforcement officers in the US state of Louisiana have been arrested in the shooting death of a 6-year-old boy.

Derrick Stafford, 32, and Norris Greenhouse Jr., 23, were arrested Friday and charged with second-degree murder, Louisiana State Police superintendent Michael Edmonson said.

Both officers were working side jobs as city marshals in the central Louisiana town of Marksville where the fatal shooting took place, Edmonson said.

Jeremy Mardis, who had been diagnosed with autism, was shot in the head and chest five times and his father was severely wounded after the officers opened fire on their vehicle on Tuesday.

"I can tell you, as a father, it was one of the most disturbing things I've witnessed," Edmonson said. "Extremely disturbing, and it is partly why we are here tonight."

Edmonson did not detail Friday exactly what is believed to have occurred the night of the shooting but officials have said the city marshals shot at a vehicle "at the conclusion of a pursuit."

Jeremy is the youngest victim of US police brutality this year. His death adds to the growing criticism of police violence against suspects.

More than 1,010 people have been killed by police since the beginning of 2015, according to data collected by an activist group known as Killed by Police.

US police brutality and racial discrimination has triggered large-scale protests and riots over the last two years.