Around 7:00 a.m. on Saturday, March 27, 1999, Border Patrol Agent Stephen M. Sullivan was transporting a group of aliens on the Otay Truck Trail when his vehicle overturned and rolled down an embankment. Three of the aliens, who had been thrown from the vehicle, climbed up out of the embankment and approached another Border Patrol agent, stating that others were still inside the vehicle and had been injured.

​

Four people, including Agent Sullivan, were killed in the accident. Agent Sullivan began his career with the Immigration and Naturalization Service as an Adjudications Officer in Los Angeles. He was hired by the Border Patrol in September 1997. At the time of his death, he was assigned to the El Cajon Station in the San Diego Sector.