Farmer Dale Murden has little doubt they were Mexican drug traffickers.
"They hide stuff in there," Murden said of the dense sugarcane crops, some as high as 14 feet. "It was very intimidating for my guys. You got men dressed in black, looking like thugs and telling them to get back."
Texas farmers and ranchers say confrontations like these are quietly adding up. This month the Texas Department of Agriculture, going beyond its usual purview that includes school lunches and regulating gas pumps, launched a website publicizing what it calls a worsening situation "threatening the lives of our fellow citizens and jeopardizing our nation's food supply."
However, some Texas Democratic lawmakers say the danger is being wildly overstated, and U.S. Border Patrol officials said they are not aware of landowners in the Rio Grande Valley facing increasing threats.
The launch last week of ProtectYourTexasBorder.com also left the state somewhat embarrassed after the site's message board quickly filled with postings calling for vigilante justice and the killing of illegal immigrants. The postings have since been removed.
Texas Agriculture Commissioner Todd Staples, a Republican in the job once held by Gov. Rick Perry, condemned those postings Thursday. But he said they shouldn't detract from the site's goal of getting more federal resources to the Texas border.
"The website demonstrates in undeniable form that greater federal government presence is needed. We need to keep this as a lookout post," Staples said.
But Texas state Sen. Jose Rodriguez said the site is misleading, lacking any data that puts the incidents or danger in context.
"For the site to convey the impression that we are under a serious threat and that there's all this concern, including to the food supply, it's just total exaggeration of reality," Rodriguez said. "It's unacceptable."
Still, there is little doubt of increased unease on Texas border farms.
Most brazen among the reported confrontations occurred earlier this year on the sugarcane field near Rio Grande City. In February, a Hidalgo County employee was similarly threatened by three men along the border river to stop clearing brush near a canal, said Troy Allen, general manager of the Delta Lake Irrigation District.
Allen said another of his workers has taken to locking himself inside the water pump houses along the Rio Grande. If someone knocks, Allen said, he doesn't answer.
"Five years ago, if someone wanted a drink of water we'd give it to them," Allen said of illegal immigrants passing through. "We have a situation that's getting pretty serious in my opinion."
Last weekend, on a ranch adjacent to land owned by country music star George Strait, authorities said a ranch foreman was shot at by men inside a pickup truck who were found trespassing. The foreman returned fire, and no one was hurt.
Staples pointed out the bullet holes as proof of the escalating threat along the border. Webb County Sheriff's Department spokeswoman Maru De La Paz, however, said there was no evidence tying the shooting to suspected drug traffickers.
Several growers and ranchers say their jobs started becoming more dangerous about two years ago.
An Arizona rancher was gunned down in 2009 while checking water lines on his property, in what authorities suspect was a killing carried out by a scout for drug smugglers. No arrests have been made. Apart from that incident, Arizona agricultural leaders say they've heard of no direct threats toward their farmers and ranchers.
In Texas, the run-ins with traffickers are largely anecdotal. Border Patrol spokesman Mark Qualia said any confrontations would be investigated by local law enforcement, but added that landowners "haven't been expressing those feelings to us."
Staples said farmers are scared to speak out. Last week, a 2 1/2-hour meeting between Staples and about 20 farmers was closed to reporters over concern farmers wouldn't otherwise attend.
"I told (farmers) we have to tell this story so our policymakers understand the critical nature of what's being said," Staples said. "It is a process that we have to continue to tell it until we get the help we need."
The Rio Grande Valley is largely farmland, making it an almost necessary route for drug smugglers. The border fence built in the last few years doesn't run through all the farms, and even farmers with the fence worry about their safety while cultivating their crops between the fence and rivers.
Texas farmers for decades have lived - begrudgingly but unafraid - with illegal immigrants cutting through their land. But some farms say they have become more intrusive in recent years, presenting a greater threat.
One farmer, Joe Aguilar, told state officials he quit the business because of the escalating risk.
"After so many years it's upsetting, but either you move on, or it's dangerous for your family," Aguilar says in a video posted on the state's new website.
But in a 2009 interview with a local TV news station about hard times for farmers, Aguilar doesn't mention danger as why he quit. He told The Associated Press this month that financial factors also played a role in his decision to sell his land.