David Rivera, who's currently on leave from his job as a New Canaan police officer, went before a judge on criminal charges of his own Tuesday, pleading not guilty at the Fairfield County Courthouse.

Rivera is charged with illegal possession of explosives, illegal storage of explosives, illegal possession of an assault weapon, illegal storage of a firearm, and illegal transfer of a firearm. He was arrested by Stratford police on April 28 following a search of his home.

Rivera also owns Black Rock Canines in Naugatuck, which trains dogs for law enforcement agencies and individuals. Rivera's arrest warrant shows two former employees contacted law enforcement with concerns about high-grade explosives, used to train dogs the dogs, being kept at the property. They said Rivera didn't have a license for those explosives and wasn't storing them safely. One worker said explosives were kept in Tupperware and tackle boxes. When the men confronted Rivera, he moved everything to his home in Stratford, according to the arrest warrant.

Law enforcement searched the home and said they found a cache of explosives, including TNT, cast boosters and RDX. Police wrote in Rivera's arrest warrant, "Some of the explosives had begun to degrade and crystallize, indicating they were extremely unstable. All explosive material that was found in the garage was found to be unlocked." Rivera also allegedly told investigators that "he didn't need any licensing because he had a badge."

Rivera and his attorney had no comment after court Tuesday, but Rivera's legal troubles go beyond this case. Last week, Naugatuck police arrested him and Daniel Luna, the former general manager of Black Rock Canines.

The two face numerous charges including animal cruelty and illegally killing canines. They're accused of shooting dogs in the head if the animals were deemed untrainable. Police say they also had untrained young employees handling explosives and did explosives detection training at the Naugatuck Event Center, where other people were. Rivera will be arraigned in that case in Waterbury Superior Court May 18.