NEW ORLEANS - Two brothers with a history of drug arrests and suspected ties to a neighborhood gang each face 20 counts of attempted second-degree murder in a shooting that brought a sudden bloody end to a neighborhood Mother's Day parade.

The arrests by police and U.S. marshals came less than four days after gunfire scattered the crowd and wounded 20 people - 19 hit by bullets and one while trying to flee.

Akein Scott, 19, was arrested without incident late Wednesday at an eastern New Orleans residence. His brother Shawn Scott, 24, was arrested Thursday morning as he tried to flee another residence in the city, police said.

Mayor Mitch Landrieu and Police Chief Ronal Serpas hailed the police work as proof of officials' determination to end violence that mars the image of the tourism-dependent city.

"We will not let up," Landrieu said. "We are demanding that the shooting stop. And we will make sure that we do everything in our power, which I hope people now see is substantial, to make sure that we protect the citizens of New Orleans."

A magistrate judge set bond for Akein Scott at $10 million Thursday morning in the attempted murder case. Another judge ordered him held without bond pending a later hearing on an unrelated gun and weapon charge.

Shawn Scott's court appearances were not yet scheduled. His Thursday morning arrest was announced by Serpas, Landrieu and District Attorney Leon Cannizzaro at a news conference in the middle of the intersection where the shooting took place, off the beaten path for most tourists but less than two miles from the popular French Quarter. Surrounding the officials were dozens of uniformed officers and onlookers from the neighborhood.

Police said Akein Scott has been identified by an unnamed witness as the person seen on a surveillance video, appearing to fire into a crowd that scatters as some fall. Shawn Scott's role in the shootings remained unclear.

Police have yet to outline a motive, other than to say it appears related to gang activity, which Landrieu called a major factor in street violence.

"This small number of people in gangs and groups are responsible for the overwhelming number of murders and shootings in this city. They are in fact terrorizing our streets," Landrieu said.

Police said the Scotts are members of a gang called the Frenchmen and Derbigny Boys.