BATON ROUGE, La. — Law enforcement officials said here Tuesday that they were investigating a plot by four people to shoot at police officers, and they cited the threat to explain the heavy police presence at protests within the last week.

The discovery of the plot arose from arrests made in connection with the burglary of a pawnshop early Saturday, federal, state and local officials said.

Eight handguns were taken, six of which have been recovered. Of the four people thought to be involved, three, including a 13-year-old, have been arrested, officials said. Another man who had bought a stolen weapon had also been arrested.

The Baton Rouge police chief, Carl Dabadie Jr., said that one of the suspects, Antonio Thomas, 17, was arrested fleeing the scene, after he and others had allegedly broken into the shop through the roof. The chief said that Mr. Thomas had said during questioning after his arrest “that the reason the burglary was being done was to harm police officers.” On Sunday, another suspect, Malik Bridgewater, 20, was arrested at his home.