Shauna Saxton said she was out driving with her family when the chaos erupted.
"I looked over my shoulder to (the) left and a gold car pulled up, and the man was there and he had a very large gun and it was pointing at me," Saxton said.
The shooting spanned the West Texas cities of Midland and Odessa on Saturday afternoon, according to Odessa Police Chief Michael Gerke. A total of 21 people were shot, and the gunman is among the dead.
READ MORE: At least 5 people killed, 21 injured in Midland-Odessa shooting in West Texas
Odessa police said Saturday afternoon that they were looking for at least one suspect who was "driving around Odessa shooting at random people." Saxton said when she saw the suspect, she began yelling at her husband in a panic.
"I was just like, 'There's a gun! He's got a gun! There's a gun!' and that's when it hit me, what those sounds were," she said.
Saxton said that was the moment she made direct contact with the suspect.
"He was looking at me," Saxton said. "I saw his face. I saw that weapon. The only thing I could think about is my little grandson in the backseat. I just thought 'Oh my God, what if something happened to him?'"
The situation began when the unnamed suspect shot a Texas Department of Public Safety trooper who had pulled him over after 3 p.m. local time, police said. The shooting set off a chaotic afternoon in which police reported that a suspect hijacked a U.S. Postal Service vehicle and began firing at random, hitting multiple people.
"Frankly, at the moment, I was just really running for my life," Saxton said. "We came back home and all this time, we're trying to process what this guy was doing, and then we find out that it was a random shooter, and we got really lucky."
Odessa is about 20 miles southwest of Midland. Both are more than 300 miles west of Dallas and lie along Interstate 20 approximately at the midpoint between El Paso and Fort Worth.
"Somebody tried to kill me today," Saxton said. "They weren't successful, but I was their target, and now, I'm just like, 'What do you do with that? How do you process that?'"
The shooting comes just weeks after a gunman in the Texas border city of El Paso killed 22 people after opening fire at a Walmart. Governor Greg Abbott this week held two meetings with lawmakers about how to prevent more mass shootings in Texas.