New Jersey State Police say they're investigating the death of 19-year-old rodeo rider Coy Lutz as an accident, although an animal rights activist group is calling for a criminal investigation.

State Police Sgt. Jeff Flynn told New Jersey 101.5 that based on a preliminary investigation into the professional bareback rider's death, "nothing at this point in the investigation points to criminal activity," Flynn said.

Lutz fell off his horse and was trampled to death Saturday at the Cowtown Rodeo in Woodstown, Salem County.

Activist group SHARK (SHowing Animals Respect and Kindness), in an open letter to State Police Superintendent Col. Joseph R. Fuentes this week, alleged it is "highly likely that the horse was stimulated with an electro-shocking device in order to cause the animal pain and make him respond wildly," prompting the trampling.

The group presented no specific evidence a shocking device was used on Lutz's horse. Instead, it pointed to what it said was a history of use at Cowtown — but at least some of that history is in dispute.

If an electric shocking device was used, the group wrote, "then the death of Coy Lutz cannot be seen as an accident but as the result of an intentional act and criminal negligence."

The group points to the June 29, 2013 death of a horse named Duke at Cowtown, filmed by one of SHARK's investigators. The group alleged a electro-shocking prod called a "Hot Shot" had been used on Duke, leading to his deat.

But NJSPCA spokesman Matt Stanton told New Jersey 101.5 his group had been involved in the 2013 investigation, and found no evidence the Hot Shot had been used.

"We took a really hard, aggressive look at it," he said. That included reviewing footage by SHARK in which the group says a Hot Rod can be seen — though it's not clear in the footage if it was used.

The SHARK video:

Cowtown's owners declined a prod was used at the time as well. The Professional Rodeo Cowboys Association forbids the use of prods on any animals inside chutes, as Duke was. Cowtown's owner told NJ Advance Media at the time his riders do have such prods, but only for emergency use such as in cases where a cowboy's life is endangered.

The state Department of Agriculture, which headed the 2013 investigation and which oversees rodeos, has not yet returned a call seeking comment.

SHARK, in its open letter, also says it has footage of a Hot Rod being used in 2008 at Cowtown.

The rodeo has not yet returned a call for comment, but a worker who picked up the phone read a statement expressing condolences to Lutz's family.

Stanton described Shark as a "very aggressive" activist organization.

Capt. Stephen Jones, the New Jersey State Police communications director, said in an email to New Jersey 101.5 the NJSP had not yet received SHARK's letter.

"When we receive it, we will determine whether the information adds to the pertinent facts in the tragic death of Mr. Lutz," he wrote.