A routine tree-trimming run in San Marcos turned deadly after authorities say a man with a knife jumped onto a moving Freightliner truck last Saturday, tried to seize control of the vehicle, and was fought off by the driver. The suspect fell into the roadway, was rushed to a hospital with a serious head injury, and died two days later, on Monday. The San Diego County Sheriff's Office has identified him as 56-year-old Mark Douglas Heninger. Homicide detectives have now taken over the case and say they still do not know why the man targeted the truck.
San Diego County Sheriff's Office officials said deputies were called to the 200 block of S. Pacific Street, where paramedics found an adult male suffering from severe head trauma. According to the sheriff's account, the man was armed with a knife when he leaped onto the driver's side running board of the truck, sparking a physical struggle. The driver called 9-1-1, stayed at the scene, and declined medical treatment after sustaining only minor injuries.
Investigation Under Way
As reported by The San Diego Union-Tribune, homicide detectives are now combing through surveillance footage and waiting for the Medical Examiner's Office to determine the cause and manner of death. Sheriff's Lt. Juan Marquez told the paper that the circumstances and motive surrounding the incident remain under investigation. In other words, detectives are still trying to piece together what, if anything, led up to the confrontation before the man grabbed onto the truck.
Not An Isolated Problem
While investigators work this case, the sheriff's office is already dealing with a broader carjacking problem around North County. Officials say they have issued multiple carjacking notices this spring and summer, including a May 21 incident in San Marcos that ended with a suspect under arrest. A San Diego County Sheriff's Office release from that date describes an armed demand for a vehicle in the Old Spaghetti Factory parking lot, followed by an ASTREA helicopter and K-9 search that ultimately led to the arrest of the suspect.
What Comes Next
Detectives are asking anyone who might have seen the July 18 struggle or has related information to call the Homicide Unit at (858) 285-6330 or Crime Stoppers at (888) 580-8477. As of now, there have been no public reports of any charges connected to the driver of the truck. Investigators say they will share more details once the Medical Examiner and homicide detectives finish their work and clarify exactly how and why the confrontation turned fatal.
