A motorcyclist racing east on Interstate 70 early on July 4 was shot in the head amid a hail of bullets fired from a Ford pickup truck in pursuit, Denver police say — and two men have been arrested in that killing. Denver police officers over the weekend arrested Cesar Ramirez-Rivera, 21, and Nelson Miranda-Rivas, 25, who were jailed for investigation of first-degree murder, according to arrest affidavits reviewed Monday by The Denver Post. The motorcyclist went down on I-70 near the east end of a tunnel around the intersection with Colorado Boulevard at 12:22 a.m.