Arizona
The shootings have caused anxiety for motorists using the stretch of I-10, the southernmost transcontinental highway in the United States, which runs through the Phoenix metro area.
In Zion National Park, four people died and three were missing after going to explore canyons, officials said.
Eight people are confirmed dead, and another five are missing.
"It's just a matter of time, if this continues, that we have tragedy on our roadways."
WHAT'S HAPPENING
Authorities urged motorists to be on guard and report any suspicious activity.
"It might not be enough to solve all of our schools' budget problems, but it will help immensely."
"I know that change can be difficult."
"Do you know that there are schools that train children your age to be suicide bombers?"
The Peoria, Arizona, police department is investigating the incident.
A beautiful and moving tribute.