Evidence that started a criminal investigation into allegations of animal abuse and drew the ire of a grocery giant was discovered by accident, the founder of animal advocacy group Animal Recovery Mission said.

The group, which has worked with law enforcement on undercover investigations in the past, had just started a factory farm division and decided to look into the dairy industry, founder Richard Couto said.

In August, the group focused on its home state of Florida and applied to various dairy jobs in Okeechobee County. One of its members was hired at Larson Dairy Inc., which supplies milk to grocery chain Publix.

"The abuse just so happened to occur on day one, hour one," Couto said. "It usually takes weeks or months to even see that sort of abuse."

After three weeks of undercover investigation, Couto said his organization gathered hundreds of hours of video evidence to support allegations of abuse of cows on the dairy farm.

The group alleges farm employees mistreated cows by kicking and hitting them, sometimes with weapons, excessively used cattle prods and contributed to poor living conditions for the animals, according to a post on its website.

Some of that evidence arrived at the Okeechobee County Sheriff's Office on Thursday morning via an express mail package. That afternoon, Sheriff Noel Stephen announced his office would be starting a criminal investigation into the allegations at the dairy farm.

Stephen, who said he'd known the Larson family for some time, said the owners welcomed the investigation. He said they already fired one worker and placed two more on suspension pending an internal investigation by the company.

Couto worries that may not be enough.

The Larson family could not be reached for comment by TCPalm on Thursday or Friday, but Jacob Larson released a statement to The Associated Press:

“We have strict protocols involving animal care and clearly the behavior shown in this video goes against everything we stand for and will not be tolerated,” Larson told the AP. “The employee involved and featured in the video has been terminated. Further corrective action will be taken if necessary as we continue to analyze the video and conduct an on-farm investigation.”

Though they're not taking an active role in the sheriff's investigation, representatives of the Florida Department of Agriculture and Consumer Services said the agency would keep an eye on it.

"The Okeechobee Sheriff's Office is currently investigating this matter, and we will provide any support we're able to, as needed," department spokeswoman Jennifer Meale said in an email Friday afternoon.

Publix announced Thursday it would be dropping Larson Dairy Inc. as a milk provider after the sheriff announced his investigation into the allegations of animal abuse, according to the Lakeland-based company's Twitter page.

"We are aware of the undercover video taken at Larson Dairy and are shocked and disturbed by the cruelty shown toward the animals. We are suspending raw milk deliveries from that farm," the grocery chain's main account tweeted.

Couto said Animal Recovery Mission plans to bring video footage of the alleged abuse to representatives in the grocery company.

This isn't the first time the group has spurred an investigation in South Florida. In late 2015, the group worked with law enforcement in Miami-Dade County on an investigation into a slaughterhouse, according to a statement from the South Florida SPCA.

The group has also investigated other slaughterhouses, animal sacrifices, bestiality and race horse abuse among other subjects, according to its website.

"We're good at what we do, and we do not stop until we get all of the evidence," Couto said.

Follow Bohatch on Twitter: @emilybohatch