One person was wounded Friday in the course of a suspected illegal arms transaction in the eastern city of Santa Cruz, Bolivian authorities said.
The incident took place around 11 am near the city zoo and remains under investigation, police Col. Walter Miranda told reporters at the scene, adding that officers had cordoned-off a nearby residence where two handguns were found.
He said that the shooter, thought to be a Brazilian, "reacted" to something by firing his weapon.
The wounded man, apparently a plainclothes police officer, was taken to a hospital, while the man who "acknowledged that he fired the shot" was arrested, according to Miranda.
The shooter expressed regret over his action to the officers who took him into custody, the colonel said.
A witness identifying himself as Rolando F. told reporters that he saw two men with a black backpack and that one of them pointed at someone in a passing vehicle.
Rolando said he heard shots and saw a man fall to the ground crying out in pain, while the two men with the backpack ran and took refuge in a nearby pharmacy.
A video posted on social media by another witness shows a young man lying on the ground with blood on his pants, surrounded by onlookers as he waited for paramedics to arrive.