It was a crime spree that killed nine people, stumped the police for months and left residents of Phoenix unnerved.

On Monday, the authorities in Arizona announced that they had arrested a 23-year-old man in what came to be known as the Serial Street Shooter case.

At an afternoon news conference, Jeri L. Williams, the Phoenix police chief, said the authorities had linked the shootings to Aaron Saucedo, who has been in police custody since his arrest on April 19 in the first of the nine killings.

He was rebooked on Monday into Maricopa County jail on 26 additional felony counts, including eight of homicide, three of attempted homicide, and several of drive-by shooting and aggravated assault, Chief Williams said.