On Saturday, July 18, 2026, Deputies from the San Marcos Sheriff’s Station responded to a report of a traffic collision with unknown injuries in the 200 block of S. Pacific Street in San Marcos.
Upon arrival, deputies and paramedics located an adult male in the roadway suffering from severe head trauma. He was transported by paramedics to a local hospital for medical treatment.
The driver of the involved vehicle remained at the scene and provided a voluntary statement to investigators. According to the driver, an adult male attempted to forcibly take his Freightliner tree‑trimming truck while the vehicle was in motion. The man reportedly jumped onto the driver‑side running board while armed with a knife. A physical altercation ensued, during which the man fell from the truck and landed on the roadway. The driver immediately called 9-1-1 to report the incident. He sustained minor injuries, declined medical attention, and was released at the scene. At this time, alcohol or drugs do not appear to be factors related to the driver.
Despite all efforts by hospital medical staff, the individual succumbed to his injuries and was pronounced deceased on Monday, July 20, 2026.
The deceased has been identified as 56‑year‑old Mark Douglas Heninger, a resident of San Diego County. Mr. Heninger’s family has been notified.
Homicide Detectives assumed responsibility for the investigation. This investigation remains ongoing. The cause and manner of death will be determined by the Medical Examiner’s Office.
The circumstances and motive surrounding the incident remain under investigation. Based on information gathered thus far, this appears to be an isolated incident, and there is no known threat to the community.
Anyone with information about this incident is asked to call the Homicide Unit at (858) 285-6330/after hours at (858) 868-3200. You can remain anonymous by calling Crime Stoppers at (888) 580-8477.
