"Wildlife Services need to be held accountable for both their animal control methods and use of taxpayer dollars," Campbell said in a statement.

"The investigation … would force Wildlife Services officials to start answering the questions they have been ducking and shed a bright light on the agency as a whole," Campbell added. "They would finally have to open their books, disclose their methods and account for their actions."

Asked for comment, agency spokeswoman Carol Bannerman said Friday by email: "At this time, Wildlife Services has not been advised of a formal request for a Congressional oversight hearing, so speculation regarding that would be inappropriate.

"An objective review will show that more than 80 percent of Wildlife Services interactions with wildlife is solved with nonlethal methods, that the majority of lethal targets are invasive species and that the tools used are 90 percent selective," Bannerman added.

At the state level, the Texas Department of Agriculture cited a Wildlife Services employee on June 6 for violating three M-44 use restrictions, including placing cyanide "in areas … where exposure to the public and family pets is probable," in the case in which the dog died near Abilene. It also noted he was working outside his territory on a cattle ranch leased by his father.

"This investigation is incredible," said Brooks Fahy, executive director of Predator Defense who has monitored M-44 poison cases for more than two decades and helped draw attention to the incident.

"What's so glaring is he is using federal funds that you and I are paying to do work on his father's leased land who also happens to be a county commissioner," Fahy said.

The employee, Kyle Traweek, could not be reached at his office by The Bee last week. Bodenchuk, the state Wildlife Services director, said Traweek had approval to work on his father's ranch and that he disputes the violations. "He does not agree that exposure to the family and pets was probable," Bodenchuk said. "This is a very unfortunate situation," Bodenchuk said. "I wish the Walker's dog had not pulled the M-44 device."

A state investigator found that the employee placed several M-44s on ranch land "less than six-tenths of a mile from Ms. Walker's house near roadways that Ms. Walker, her family and the family's dog frequently traveled."

Angel Walker said she did not know the M-44s had been deployed near her house until she came home one Friday afternoon and saw a sign on a gate. By then, it was too late.

She and her husband finally found their dog – a young pit bull named Bella – on Sunday morning about 90 feet from an M-44.

The Walkers said they support the congressional bill that would ban M-44s.

"It's random killing," J.D. Walker said. The devices attract "any animal that might possibly eat meat. … You're talking about coons (raccoons), possums (opossums), a fox. A fox is no danger to a cow. A coon is no danger to a cow. A possum is definitely no danger to a cow."