Having driven this stretch of I-40 in Arizona many times before I know from first hand experience how treacherous the hill west of Williams can be in snowy weather. Unfortunately this time the accident that occurred was extremely deadly:

Arizona officials are working to determine whether additional human remains discovered in the debris of a fatal pileup crash on Interstate 40 on March 13 are those of the South Korean family who went missing in the area at the time of the crash.
Jiyeon Lee, Taehee Kim and Junghee Kim have been missing for nearly two weeks after driving through a winter storm on their road trip between the Grand Canyon and Las Vegas.
Investigators have confirmed that one of the vehicles in the collision, which involved multiple passenger vehicles that “were rear-ended, pushing them into, and in some cases, underneath crashed tractor-trailers,” was a BMW SUV, an update from the Coconino County Sheriff’s Office said on Monday. The family had been traveling in a BMW rental vehicle, the sheriff’s office said.
You can read more at the link.