SAN FRANCISCO (KRON) – The San Francisco Police Department has released new details surrounding their months-long investigation into a tour bus crash in Union Square last November. The massive wreck left more than a dozen people injured, several cars damaged, and at least six people suffered life-threatening injuries.

The operator of the bus, Kenneth Malvar, 53, of San Francisco, was issued a citation for the unsafe speed violation, police said.

“The inspection conducted by the CHP Multidisciplinary Accident Investigation Team (MAIT) revealed that there were no mechanical issues found in the

bus’s braking, steering or throttle systems to explain the bus’s acceleration or inability to stop. Investigators determined the primary collision factor was unsafe speed (22350 California Vehicle Code) and the incident was caused by operator error,” the San Francisco Police Department said in Collision Investigation report.

The incident happened Nov. 13, at around 3 p.m. in the 200 block of Stockton near Post Street in Union Square. Police said the bus started picking up speed in the 500 block of Post Street and then ran into the scaffolding and cars shortly thereafter.

19 people were injured when the double-decker bus lost control, struck a pedestrian and cyclist, crashed into a dozen cars then slammed into a construction site. Scaffolding at the site crashed down on the sidewalk and street pinning several vehicles under the debris.

The bus operator, a bus employee, and two bus passengers were among those injured. The remaining injured parties were the bicyclist, four pedestrians and ten persons from the other involved motor vehicles. Two other passengers on the bus did not claim injury. At the time, at least six of the injured were considered to have suffered life threatening injuries.