A 22-year-old man has been charged with fatally shooting seven people and wounding an eighth in a seven-week span that spread from New Jersey to Pennsylvania, punctuated by bursts of violence that left multiple people dead within several hours.

The man, Todd West, of Elizabeth, N.J., led police officers on a frantic chase, sometimes shooting his next victim before investigators had wiped the asphalt of the last person’s blood, the authorities said on Thursday.

His motive remained unclear, as did the method he used to choose his targets, but the authorities in Union County, N.J., called the carnage he left behind “horrific.”

The police pursued him for 20 hours in Elizabeth on June 25, moving from one crime scene to another as Mr. West killed three people with his .38-caliber revolver within several blocks, the authorities said. The police were a step behind, as Mr. West fled to Pennsylvania, where, on July 5, the authorities said, he shot and killed a man in Easton about an hour before killing two more people in Allentown. He was arrested there on Monday.