Two children are dead and their mother is behind bars suspected of driving under the influence following a crash in Napa Sunday morning, the California Highway Patrol said.

The crash site sits along a bustling corridor for traffic heading onto the highway or deeper into Napa, with a gas station to the north and a park-and-ride to the south. The offramp, lined with scattered trees and plants, was shut down until noon as investigators worked to determine how fast the sedan was traveling before impact.

A good Samaritan, who was helping out another driver, was killed in a suspected DUI crashes Sunday morning. The California Highway Patrol responded to Highway 99, north of the westside Boulevard in Atwater of a reported seperate crashes.