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A 27-year-old man killed his mother and drove about 200 miles through the Mojave Desert before he was fatally shot by police on a freeway, stranding motorists for up to 19 hours and backing up traffic for miles on the main route between Southern California and Las Vegas, authorities said.

The investigation began Wednesday when Kern County deputies found 55-year-old Guadalupe Adams dead with “traumatic injuries” in Tehachapi, which is about 35 miles (56 kilometers) east of Bakersfield.

Kern County deputies believed an “armed and dangerous” man — identified as the woman’s son, Madison Adams — driving a 2017 Nissan was involved in the killing and asked the San Berndardino County Sheriff’s Department to watch out for him.

Officers from the California Highway Patrol found the Nissan stopped on the freeway’s shoulder in Nipton, which is near the Nevada state line. Authorities from CHP, San Bernardino and the Nevada Highway Patrol conducted a “high-risk” traffic stop.

Officers from each agency opened fire, according to San Bernardino sheriff’s spokeswoman Cindy Bachman. Madison Adams was pronounced dead at the scene.

The motive behind the killing was not immediately disclosed.

Bachman did not have details about the circumstances surrounding the shooting on Thursday, such as if Madison Adams was armed when he was shot.

The investigation closed the northbound Interstate 15 on the California side through 3 p.m. Thursday and caused a backup between 5 and 8 miles (8 and 12.87 kilometers) long. Some motorists were forced to sit at the roadblock through the night and much of Thursday.

Montgomery Granito, of Los Angeles, told The Las Vegas Review-Journal that he and his family waited in their vehicle for nearly seven hours at the roadblock from Wednesday evening to Thursday morning before they learned that drivers were being diverted at an exit miles earlier. He said law enforcement never spoke to drivers stuck there and he finally crossed the median Thursday morning to the freeway’s southbound lanes to head back.

He told the newspaper that 30 to 60 vehicles sat at the road block all night and many were still there when he left Thursday morning.

Kevin Shea told the newspaper he was stranded on the freeway for more than an hour early Thursday as he tried to drive from Southern California to Las Vegas. He said Google Maps only showed a 24-minute delay.

The California Highway Patrol’s online traffic log reported that two vehicles ran out of gas on the freeway.

Guadalupe Adams, known as “Lupe,” had worked for the California Department of Corrections and Rehabilitation since 2006. She was an office technician at the California Correctional Institution in Tehachapi at the time of her death, according to the department.