MCALLEN, Texas — Seconds after the radio crackled and the government SUVs sped into the darkness, Border Patrol agents sprinted through the brush and toward the border in an all-too-familiar pursuit of drug smugglers.
"They dropped their bundles of narcotics and went back into Mexico," said agent Marlene Castro, sounding disappointed after racing through a pitch-black clearing outside Rio Grande City. Still, on this recent night, agents would recover 66 pounds of marijuana with a street value of roughly $53,000.
But chasing drug smugglers wasn't the only thing keeping them busy.
During two days that NBC News spent with U.S. Customs and Border Protection officials, it became clear that Castro and her colleagues were dealing with a sudden surge of families from Central America who are running toward those officials — not from them.
Scenes from the U.S.-Mexico border:
Many of the families are eager to be caught so they can apply for asylum or temporary protected status as they try to escape the violence back home.
Apprehensions on the Southwest border, along the Rio Grande, are rising. There were 46,195 in October — that was almost 20,000 more than the same month two years ago and the largest spike since the massive surge of unaccompanied minors during the summer of 2014.
Castro said the biggest difference this time around is that the Border Patrol is better equipped to deal with the influx. A new processing center has the capacity to hold 1,000 migrants at a time. In November, the federal government even sent 150 more border patrol agents to the McAllen area in the southern tip of Texas.
Wall already built along the border:
"Some people sell everything they own to make the trip over here," Castro said. "They run the risk — the women, of getting raped; the men, of being robbed — and they still come over here."
And if the flow seems never-ending, so does the debate over how best to secure the border.
During the presidential campaign, Republican nominee Donald Trump promised to build a "big, beautiful" wall to stop the flow of immigrants crossing the border illegally.
He referred to some of the Mexicans coming into the country as "rapists" and in a testy exchange during one presidential debate, he called some of the migrants "bad hombres" who should not be here.
Since winning the election, Trump has said he would begin to tackle the issue bydeporting 2 million to 3 million undocumented immigrants with criminal records, although he has not offered specifics on how that would happen.
In Texas, spending over border security has become increasingly controversial. Extra troopers who assist the Border Patrol are reportedly costing taxpayers $800 million during the current two-year budget, and the Texas Department of Public Safety is asking for another $1.1 billion to expand the border security effort.
Scenes from the northern border:
Rio Grande Valley Border Patrol Sector Chief Manuel Padilla told NBC News that a brick-and-mortar wall is only part of the answer.
"I never look at one singular solution to a very complex problem," he said. The solution "includes aircraft, it includes technology, and in some places, the fence is absolutely necessary."
A 3-year-old girl and 5-year-old boy stand at the feet of their mothers, who say they made the long journey to the U.S. from El Salvador. David Douglas / NBC News
At the Sacred Heart Church, Sister Norma Pimentel and her volunteers are helping more than 300 migrants a day. Many of them wear ankle monitors as they await immigration court hearings.
She said a wall wouldn't address the root cause of the influx: violence and poverty in Central America.
"There's no justification to send back people that are hurting that more than likely will end up getting killed back home," Pimentel said.
Francisca Cecilia brought her 5-year-old son, Christopher, on a harrowing three-week journey from El Salvador after she said a street gang murdered her nephew.
Choking back tears, she described to NBC News in Spanish how she was hoping to stay in the United States despite having illegally crossed the border.
"We're all human," she said.