What he saw this time was a car heading north toward him on the freeway, still half a mile away. Suddenly the car made a U-turn through a rest area and returned onto the freeway heading south.

“Strange,” Pompa said, running through the possibilities in his head. The car was a Mazda compact, impractical for transporting a big load of illegals, but he had found 10 people in cars like that before. Its back bumper looked heavy and the windows were dark. Plus, why would anyone turn around like that in the middle of the freeway, unless they had spotted his police car and chosen to avoid him?

Pompa accelerated onto the freeway, turned on his lights and raced to catch up with the Mazda. “I have a 1080, possible pursuit,” he radioed. He pushed his car to 75, 85, 90, until finally the Mazda came into view a few hundred yards in front of him. It sped away and Pompa pressed his accelerator to the floor. The Mazda swung around a truck and Pompa followed.

He had been in more than 50 chases in the past six months, and at first his hands had gotten sticky against the wheel and dispatchers had teased him for sounding nervous and shrill on the radio, like a balloon leaking air. But he’d had enough practice now to calm himself and think tactically about scenarios, none of which were good. His aging car was incapable of going beyond 97 mph, and six drivers had simply outrun him in chases. He had no available backup, and no time to call for it anyway. If he pursued the Mazda too hard, he could cause its driver to crash and kill whoever was inside, maybe a load of Central American children. If he fell back too far, the car would be gone, along with the weapons or drugs that could be inside.

“Come on, come on, come on,” he said, staring at the Mazda, urging it to the side of the road, and a few seconds later the car swerved toward the brush on the right side of the highway. The driver jammed on the brakes. A back door flew open as the car continued to move and seven people piled out: four men, two women and a child, with little water and no supplies. They tumbled onto the shoulder of the road, raced into the brush and climbed over a barbed-wire fence onto a desolate ranch. Then the Mazda tore back onto the highway.

“Damn it,” Pompa said, because now as the only deputy on duty in Brooks County he had to make a choice: Head off, alone and on foot, after seven people in the brush? Or chase after the car and whatever was still inside? He pressed down on the gas.

The Mazda raced to 90 mph and then, less than a minute later, swung wildly again to the side of the road and stopped. The driver opened his door and started to run, leaving the car running, too.

“Damn it,” Pompa said again, because now came another choice: Deal with a running car obstructing the right lane of a major freeway? Or chase this man wearing a baseball cap and jeans, probably an experienced coyote who was younger, faster and better at navigating the brush?

Pompa thought about the calf muscle he had torn in a chase a few months earlier, and how he had no health insurance to cover that injury, and how he had been unable to take sick time to heal because there was no one to fill in for him. “Should I go after him?” he said, but instead he watched for a few seconds as the man climbed over a 10-foot fence and disappeared into tall grass.

Pompa left his police lights flashing and went to search the car, which was empty except for a water bottle and a rental car contract from McAllen. He called a friend who worked for a tow truck company and asked him to impound the car. “I got another one for you,” Pompa told him, before recounting the chase.

“Great police work,” the friend said.

“I guess,” Pompa said, but now seven more people were in the brush, including a child who might make it to where he was going or maybe die trying. The smuggling guide was probably on his way back to Mexico to pick up his next load. There was a car on the side of the road that by law would be returned to the rental company, which would rent it out again. “It’s like catching air,” Pompa said.

He took out his phone and snapped a picture of the car for his records. “I need to remember it,” he said, because it probably would be loaded up again soon and driving back through Brooks County, where it would be his job alone to find it.