The 37-year-old victim rear-ended a pickup truck that was slowing for a stoplight at the intersection of East El Norte Parkway and North Rose Street in Escondido about 7:15 a.m., according to the county Medical Examiner's Office.
The impact sent him tumbling onto the roadway, where he was rolled over by the rear wheels of a tractor-trailer. The trucker, not realizing what had happened, did not stop, police Officer Tyler Songer said.
The motorcyclist died at the scene of the accident. The Escondido resident's name was withheld pending family notification.
Police went to area businesses frequented by commercial cargo drivers and found the semi that had been involved in the fatality.
"Further investigation revealed that the (trucker) was not aware he was involved," Songer said. "Charges will not be filed in this case."