ROMA, Starr County - The U.S. Border Patrol agent had not seen an undocumented immigrant in hours, so when he heard that a nearby camera had spotted 15 people preparing to sneak into America, he grabbed his radio and pressed it to his ear.

"Here we go," thought Agent Jose Luis Perales. He stopped his truck a few miles northwest of the group, at the top of a hill overlooking a sea of arid ranchland.

Perales was built like a linebacker at 6 feet tall and 235 pounds, but his 16 years in the Border Patrol had taught him it would take more than physical power to catch the group after it crossed. Multiple agents would have to converge at just the right moment: Pouncing too soon would allow the migrants to dart back into Mexico and regroup for another try. Moving too late would let them disappear into this town an hour west of McAllen - possibly with illicit drugs.

He had nearly four hours until his shift would end at 10 p.m., but on this late July evening, Perales would not have to wait long.

Within minutes, an agent watching the migrants radioed that they had crossed the border and that a white van was creeping toward them.

"I think that was the load vehicle," the agent said.

Perales put his hand on his truck's gear shift, waiting for a signal to hit the gas.

"Come on," he whispered.

No signal came, however. Instead, the radio reported that another vehicle was driving toward the migrants - a Texas state trooper's cruiser.

The trooper had not notified the Border Patrol, leaving the agents to wonder what was happening.

"He's driving down there," Perales repeated to himself. "What for?"

It was a scene that could occur only in Texas, the only state in America that spends a significant amount of its own money to guard the same line as the Border Patrol.

The state has spent $950 million since 2005 on troopers, cameras, spy planes and gun boats, including $124 million on a year-old surge ordered by former Gov. Rick Perry in response to last spring's wave of unaccompanied minors crossing the border.

Still, Perales found the trooper's presence unusual. The state largely had left the border itself to the federal agents, focusing instead on the main East-West highway in Starr and Hidalgo counties. Troopers could not inquire about immigration status, so they stationed their black cars virtually every half mile on Highway 83, pulling people over for minor traffic violations, scanning stopped vehicles for suspicious cargo and calling the Border Patrol to make citizenship inquiries.

Agents and troopers had access to the same motion-activated cameras, but they did not talk by radio.

Sitting in his truck, Perales could not help wondering if the trooper's sudden arrival was a sign of things to come.

A month earlier, in June, lawmakers had boosted border security funding to an unprecedented $800 million over the next two years. The sum included $116 million to hire a border-based Texas Rangers company, 250 troopers - including 52 who would be commissioned in August - and 110 support staffers, as well as $143 million to pay troopers statewide to work 50 hours per week.

Another $72 million would be used to keep some Texas National Guard troops on the border, while $35 million would be distributed in grants to local law enforcement agencies, $17 million on a new crime reporting system, $7.5 million for a new spy plane, $6 million for new operation centers and $3 million for more cameras.

State officials said the money would allow them to expand operations, including deploying more troopers closer to the border.

Already, some were questioning the wisdom of the investment. Previous initiatives had been criticized for their impact on local residents and cost effectiveness for taxpayers, but the latest splurge had spawned a new question: Could more money actually harm border security?

Many locals welcomed the spending, but others worried it could interfere with tactical Border Patrol operations, draw potential recruits from area law enforcement agencies or otherwise disrupt successful ongoing efforts.

The Rio Grande Valley, where most of the money would go, is a preferred thoroughfare for smugglers but far safer than in the past. Nationwide, there is less illegal immigration and more Border Patrol agents - including 3,000 in the Valley - than at any time in decades.

In La Joya, just west of McAllen, officials who long had supported state efforts recently drafted a resolution calling for "a better working relationship" between border security entities.

"For some reason, the communication is not there, and that really concerns us," said City Manager Mike Alaniz, adding that troopers have reduced crime, but that an increase in forces without more coordination could undermine the progress. "When it comes to manpower, more is not always merrier."

Now, the concerns were playing out in front of Perales. He was not surprised to hear his radio report what the migrants did when the trooper drove toward them.

"I think they may have gone back." There was a pause. "They went back."

Perales exhaled. Other agents were leaving their strategic posts to look for smugglers elsewhere, but the veteran knew the group of 15 was big, and it would try again. He decided to wait.

The life of a Border Patrol agent often passes like this, with flashes of excitement surrounded by long stretches of boredom. Earlier, Perales had helped apprehend a family, given water to a man who had surrendered due to thirst and chased seven undocumented immigrants who fled back to Mexico - all in the first hour of his shift. Then it got quiet.

Now he waited, and as the minutes passed, it became clear that the group no longer was in a hurry to cross.

The radio did not give any update about the trooper or explanation for his behavior, but Perales assumed he had moved on.

The sun began to set, casting a hot orange glow over the dirt. A family of quail walked past the front of the truck.

A Border Patrol member riding with Perales took out his cellphone to play Boom Beach, a video game in which players fight for territory on an island paradise.

Stymied from defending his actual nation, he was defending a virtual one.

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When darkness fell, the agent's hunger overtook his stubbornness. It was nearly 9 p.m. Perales drove a couple miles to a Subway sandwich shop just off Highway 83.

As he parked, a black state cruiser pulled in beside him.

The lanky trooper who stepped out was dumbfounded. He had just had a chance to catch some undocumented immigrants, he said, but was surprised that no Border Patrol agents had showed up.

It was the trooper who interfered earlier, Perales realized, and he had not just driven by the migrants. He had stayed near them. No wonder they had not crossed.

"It's because we were waiting for them to come across," Perales told him in the sandwich line. "That's why."

"Oh, really?" the trooper asked.

The trooper repeated his story, as if unable to comprehend what had happened. He was in town on assignment from East Texas, he said, and he had rushed to the border after hearing that a motion-activated camera had spotted a big group coming across.

"I was sitting there waiting for y'all," he said.

"We were on the radio," Perales responded.

The trooper frowned.

"I wish I knew that."

Perales sat to eat, but he knew he could not stay long. With the trooper gone, the migrants would cross soon.

The agent finished his sandwich, got back on the road and started driving back toward where he had come from, passing trooper after trooper as he left town.

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On a dirt road by the Rio Grande River, Perales leaned out of his truck to tell the story to another agent as they waited for word on the group of migrants.

"So, we ran into him right now at Subway," Perales said. "He was like, 'Wish I knew.' "

The agents laughed.

Neither man offered his personal feelings about the collaboration between the federal and state efforts. It was not something that rank-and-file agents discussed.

Publicly, the question of collaboration exploded in May because of a letter written by the head of the agency that runs the Border Patrol. The Texas Department of Public Safety had told lawmakers that the agency was a "partner" in Perry's surge, but the official wrote it had "declined to participate" in the operation.

Democrats, who already believed DPS was harassing border residents and instilling unwarranted fear, seized on the letter, with state Rep. Cesar Blanco of El Paso saying it appeared that agency director Steve McCraw "may have intentionally misled lawmakers."

McCraw played down the dispute, calling it a matter of semantics. Federal agents work in the surge operation center, he noted, and a trooper works from the Border Patrol station in Rio Grande City.

The DPS declined requests to spend time with a trooper or see the operation center. In an interview, Commander Jose Rodriguez, the agency's top official in the region, said communication issues exist in any operation and have become less frequent in border efforts.

Rodriguez said the miscommunication in Roma sounded like it was the Border Patrol's fault.

"This particular unit that was watching didn't make the call," he said. "If they would call and say, 'Hey, have all assets clear this area,' that would occur."

The head of the Texas Border Sheriff's Coalition saw it differently. Donald Reay said in an interview that he was not surprised by the incident. He blamed the trooper.

"In that situation, the primary agency is the Border Patrol," said Reay, a longtime El Paso County Sheriff's Office official, who added that some sheriffs also were irked that DPS troopers have so little to do that they often congregate in parking lots, talking or eating tacos.

Others spoke more highly about the state efforts. Several law enforcement officials said the added presence had reduced crime. Even the chief of the McAllen Police Department, which lost eight officers to the first class of DPS troopers, said the additional manpower would make the community safer.

Also among those who praised the DPS was Perales' boss, Jason Owens, the agent in charge of the Rio Grande City station.

"This is my fifth station," Owens said, "and it's the best in terms of collaboration with locals."

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The radio interrupted the conversation by the river a few minutes before 10 p.m., just as Perales was preparing for his shift to end:

Something was happening close to where the group of migrants had been spotted hours earlier.

Perales sped his truck to the area, a neighborhood of small houses and dense brush. He hopped out into a surprisingly cool breeze, the air filled with the sound of dogs barking.

He had arrived 90 seconds after the call, but already he knew he was too late.

Later, reflecting on the incident while driving back to the station, Perales would express disappointment. He said he respected the troopers and believed most do good work, but he admitted he was not excited about the looming increase.

"In a way it makes it harder," he would say. "It's hard to say that it would make it easier, because like you saw awhile ago, we were set up for it. … If DPS wouldn't have been there, they would have come across. So, in a way they kind of hurt our operations because we were all in place to catch them."

Instead, Perales and two other agents who searched in the dark for signs of the group found only a type of rope that smugglers use to bundle marijuana.

The undocumented immigrants had not only made it into the United States. They had brought drugs.

"Damn," Perales said.