A suspect was arrested Friday in a string of shootings that have kept drivers on edge for weeks as vehicles were struck with seemingly random gunfire as they drove down Phoenix freeways. The 21-year-old man was arrested at a Wal-Mart in Glendale, a suburb west of Phoenix at about 7 p.m., said Daniel Scarpinato, a spokesman for Gov. Doug Ducey. Department of Public Safety Director Frank Milstead announced the arrest at a news conference two hours later, saying a suspect was arrested in four of the 11 shootings. He said the investigation continues. “Are there others out there? Are there copycats? That is possible,” Milstead said.