A Chandler man died Friday morning when his motorcycle crashed into an embankment at milepost 224 on Highway 87.
Mario Sanchez, 33, died at the scene, according to Officer Jason Seeger of the Department of Public Safety in Fountain Hills.
Local resident Walter Onizchak was one of the first people on the scene after the crash and recalled seeing Sanchez on the road.
"He passed me very fast," Onizchak said, "with no helmet."
Witnesses who saw the accident told officers they didn't think Sanchez was traveling at excessive speeds.
Vai Butler, a nurse at Phoenix Memorial Hospital, also was traveling on Highway 87 and stopped to help the victim.
Seeger could not say what caused the accident.
"Its an ongoing investigation right now," Seeger said. "We don't know how it happened."