DENVER (AP) — A Colorado man charged with killing his family and dumping their bodies at an oil worksite taped a video presentation six years ago about saving or abandoning relationships.

A YouTube video posted in April 2012 shows Christopher Watts giving a PowerPoint presentation that he titled "Communication Speech, Relationship Deterioration and Repair."

Watts opened the presentation by saying it is for a course he was taking.

Then he speaks of infidelity — possibly with someone at work — as a reason that relationships fail.

Police in suburban Denver say Watts was having an affair with a co-worker before he was arrested last week in the slayings of his wife, Shanann Watts, and their two young daughters. He has not entered a plea to murder and other felony charges.

According to court documents, Watts told police in Frederick, a community in the oil and gas fields north of Denver, that he told his wife Aug. 13 that he wanted to separate. A police investigation determined that Watts "was actively involved in an affair with a co-worker," the documents state.

Watts worked at Anadarko Petroleum. He was fired Aug. 15, the day of his arrest.

Watts told investigators that he killed his wife after discovering that she had strangled their two daughters, Bella, 3, and Celeste, 4, after he told her he wanted to separate.

He was charged this week with first degree murder and other felony counts in the slayings. Shanann's body was discovered in a shallow grave about 40 miles (65 kilometers) from the family's Frederick home; the girls' bodies were recovered from nearby oil tanks, according to an arrest warrant affidavit.

In the 2012 video posted online about six months before the couple wed, Watts says he is in suburban Broomfield, where the Watts family once lived.

"Sometimes you find your partner no longer attractive physically or in their personality," he says. "When you are in a relationship you have to show desire, lust toward your partner. Sometimes when you get married that the lust and the desire kind of fall by the wayside a little bit."

At another point, Watts says: "Even at the job. You might meet a new person and (it) could strengthen into something else and could weaken the bond you have with the partner you have."

"And you feel that you might be better with someone else that you've met," he declares. "You think that you can no longer do — that your partner is someone that you can't be with."

Krista Henery, a spokeswoman for the Weld County district attorney's office, declined comment about the video Wednesday. Watts' public defender, James Merson, did not immediately return a phone message.

Watts in the video cites various experts in recommending steps to strengthen and salvage relationships, including listening attentively, thinking before speaking, and openly expressing support and affection.

"Sometimes when you have children and your relationship starts to deteriorate a child could help repair it," he says.

He also lists three questions to ask when a relationship is in jeopardy:

"Do I have the desire to keep this relationship going? Do I have a moral obligation to stay in this relationship? Or is it a necessity for me to stay in this relationship?"

As Watts ends the presentation, he gets a round of applause from two women and two men seated on a sofa across the room. One of the women says, "Good job."

Shanann Watts is not seen in the video. Under a last name she had in an earlier marriage, Shanann King posted a comment to the video that said: "Great job Christopher! Good information!"

North Carolina court records show she divorced around 2009, several years before she and Christopher Watts married.

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Associated Press writer Jonathan Drew contributed from Raleigh, North Carolina.