Federal wildlife agents who last year investigated a group of Gulf coast anglers linked to a brutal shark-dragging video were foiled by uncooperative witnesses and an inability to confirm when the illegal acts occurred.

The investigation, prompted in 2015 after state wildlife officials received numerous complaints about the group, spanned more than a year and mainly focused on numerous online photos of one suspect manhandling protect species of birds, according to records released to the Miami Herald. However, the federal case, which focused on possible violations to the Migratory Bird Act, ultimately ended without charges after investigators were unable to determine when the pictures were taken.

Florida wildlife officials launched a new investigation last month after the shark-dragging video was posted, went viral and ignited online outrage that has also taken aim at MTV and one of its newest reality stars.

Authorities have not confirmed the identities of the men in the images. But after the video appeared on local shark hunter Mark Quartiano's Instagram feed, online commenters quickly identified them as belonging to a group of friends - including Michael Wenzel, Robert Lee "Bo" Benac and "Siesta Key" reality show cast member Alex Kompothecras - who have posted pictures and videos of fishing exploits that appear to violate state and federal fishing rules, and some notions of decency.

The case expanded after additional videos surfaced showing the men shooting at fish, using them for "beer bongs" and swimming with a shark in a pool, Florida Fish and Wildlife Conservation Commission spokesman Rob Klepper said Tuesday.

Kompothecras - the privileged son of a wealthy chiropractor who this weekend posted an Instagram photo of himself outside the Fontainebleu perched on the hood of a $300,000 Rolls-Royce - has drawn particular scorn. A Facebook page dedicated to boycotting the MTV show has so far collected nearly 14,000 likes and followers, about 2,000 more than the MTV page devoted to the show. A Change.org petition calling for the state to file charges has collected nearly 65,000 signatures.

Last week, Kompothecras told People magazine that he was horrified by the dragging video and had not responded to Wenzel's attempts to contact him.

The fury didn't end online. Last week, MTV canceled a premiere party after cast members told police they received threats. And Gov. Rick Scott has urged state wildlife managers to review fishing rules. The Florida Fish and Wildlife Conservation Commission holds its next public meeting in late September.

According to the records obtained by the Herald, a U.S. Fish and Wildlife Service agent opened a case in August 2015 after state wildlife officials received numerous complaints about online posts. The federal agent quickly identified the man holding white and brown pelicans, a cormorant and two gulls. The heavily redacted 47-page report omits all names, but matching online posts show it's Wenzel.

The federal agent counted six potential violations of the bird act and agreed to a joint investigation, which Klepper said was led by the federal agency.

In September, the two investigators paid a visit to the man pictured in the post, presumably Wenzel. When he "invoked his right to an attorney," they left without interviewing him.

Investigators then tried to collect information from the group of friends who appear in posts, but had little luck. They tracked down a friend, but he wasn't at home when they arrived so they talked to two others who were there but couldn't provide much help. A month later, they located another friend. The unidentified man said that in October 2014, he was hanging out on a dock in St. Petersburg with at least three men when one of them hooked a spotted eagle ray, which is protected in Florida waters.

The witness told investigators someone in the group - it's not clear who, but Wenzel and three other men are shown in online posts holding a spotted eagle ray - chopped off its wings and said he was going to freeze them. The friend then identified some in the group and passed along the name of another acquaintance who might have information.

In November, investigators tried to retrace Wenzel's steps to determine where the pictures were taken.

Using the background from a photo of him gripping a brown pelican as their guide, they motored around the coast near the Manatee River and determined the shot was likely taken at the Snead Island Crab and Fish House, a decades-old, well-known fish shack. They confirmed a second picture of Wenzel holding a gull by the neck was taken near another popular fishing spot to the west, called Seven Pines.

In December, the investigators arranged another meeting in an attempt to again talk to a potential suspect or witness. Two days later, the agent received a text from a woman, possibly the suspect's mother, saying all questions should be directed to their attorney.

The next month, the federal agent went back to social media to look for more violations and came across more images: one showing one of the suspects holding up an alligator by the jaw and a second showing a man grabbing another alligator by the tail while nine others look on. The agent passed along the posts to state investigators, who manage the protected species.

Six months later, in June last year, the records indicate the case was transferred to another federal agent. In September, the agent reviewed the case and in December 2016, after discussing it with the original agent, the investigation was closed. The report lists the inability to confirm the dates of the events, and refusal of the "main subjects" to talk without attorneys, as contributing factors.

When asked Tuesday why the case was transferred or why agents didn't follow up with attorneys, U.S. Fish and Wildlife law enforcement officials declined to comment, saying the case is closed.

Florida officials are still searching records to figure out what happened on the state's end, said Klepper, the FWC spokesman.

"It's my understanding that in 2015 we received some tips over social media posts that contained various individuals with protected wildlife. We briefly looked into that and then immediately contacted federal authorities because it was primarily violations of the Migratory Bird Act," he said. "Sometimes when we hand over cases like this to the federal authorities, a report isn't generated."

He could not say how long the state will take to complete its investigation due to "the nature of the investigation and the complexity of the investigation."

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