Mark Constantino and his wife Debby Constantino, a couple featured in episodes of the Travel Channel's paranormal investigation series "Ghost Adventures," were found dead along with a third unidentified man in Sparks, Nevada Tuesday.

The victims were found dead in their daughter's apartment after having a standoff with police, according to Entertainment Tonight. The investigation reportedly began after 8 a.m. when a woman returned home to find one roommate (unidentified man) dead and her other roommate, Debby, missing.

Police traced Debby's cell phone and found her being held hostage by Mark in their daughter's apartment, KTVN News reported. Negotiations with the gunman, who officers learned was Mark, failed. Reno police deputy chief Tom Robinson said that Mark told police, "give me 15 minutes to gather my thoughts or I'll kill her."

The SWAT team heard shots fired as they approached home, the report added. Police eventually used explosives to blow the door open and found the couple dead inside.

The couple, who were electronic voice phenomena (EVP) experts, had a history of domestic violence, according to police reports. Mark was charged with "kidnapping, domestic battery by strangulation and domestic battery against Debby" in July. Their daughter was also charged as an accomplice in the incident. Debby later obtained a restraining order against Mark. Debby was reportedly charged with domestic violence and battery with a deadly weapon earlier this year.

Fans have posted their condolences on the couple's shared Facebook page. No official statement by Travel Channel Network or "Ghost Adventures" has been released regarding Mark and Debby's death.