A man died after being hit by a car and a big-rig after standing on an Interstate 580 offramp following a confrontation with his rideshare driver, while a second pedestrian in the immediate vicinity for unknown reasons was also struck by both vehicles in Livermore on Sunday night.

The situation began unfolding around 9:20 p.m. when an Uber driver pulled over on the I-580 westbound offramp to Isabel Avenue after some sort of altercation with their lone passenger, according to Officer Tyler Hahn of the California Highway Patrol. The Uber driver left the scene out of fear for their safety and reported the incident to 911.

Meanwhile, the passenger remained standing in the unlit Isabel offramp area near the creek crossing. A second man who is currently unidentified and apparently unrelated to the Uber ride was also a pedestrian in the area, according to Hahn.

Both men ended up in the offramp lanes rather than the shoulder and were struck by a Honda Civic and then by a big-rig, according to Hahn.

The man who had been the Uber passenger died at the scene, Hahn said. His identity has not yet been revealed publicly by the Alameda County Coroner's Bureau.

The second pedestrian was transported to an area hospital in critical condition. Authorities have not yet confirmed his identity or what he was doing on the offramp. "Our big question is: Where'd that other pedestrian come from?" Hahn said.

The circumstances of the collisions remain under investigation. Neither drugs nor alcohol were suspected as factors for the Civic or big-rig drivers, according to Hahn.

Anyone who may have witnessed any aspect of the situation can contact the CHP-Dublin office at 925-828-0466.