Carbon County SWAT officers entered the home and found the Donaldsons dead in the master bedroom.
Drolc said the deaths had been ruled an apparent murder-suicide, pending autopsies.
"Depression and marital problems are the likely contributing factors to this," Drolc said Monday. "There also were some employment issues and disability issues for Mr. Donaldson."
The children, who were physically unharmed, are now in the custody of their grandparents.
Citing the ongoing nature of the investigation, Drolc declined to release further details.
However, court records show that in 2006 Shaniel filed a cohabitant abuse case against David. The case was dismissed just days after being filed and corresponding documents are sealed.
The killing came just two days after another apparent murder-suicide in Salt Lake County. Friday, officials found Felipe Rodriguez, 37, and his wife, Iris, 32, dead in their SUV on Interstate 80. The couple died from gunshot wounds, police reported.
According to UHP Cpl. Todd Johnson, the shooting resulted from a "marital issue, a relationship issue." Johnson added that Felipe Rodriguez appeared to have been the person who fired the shots.
Family members said last week that the couple appeared to be happy and there were no warning signs.
Peg Coleman, executive director of the Utah Domestic Violence Council, said that's not unusual. Coleman did not have information about the recent Utah incidents, but said troubled couples sometimes let issues "simmer and brew for years."
Coleman also said murder-suicides typically happen when there is a power imbalance in the relationship.
"Often times you'll see it where one person had a lot more control over the other person," she said.
According to a report by the Utah Office on Domestic Violence, there were 19 domestic violence-related deaths in Utah in 2010, the most recent figures available. Three of those victims were men who also killed their cohabitants. A fourth man tried to commit suicide after killing his wife but survived, the report said.
According to the National Domestic Violence Fatality Review Initiative, from 2003-2008, a third of domestic violence homicide suspects committed suicide after killing their partners. Those suspects 92.6 percent of whom were men also often had a history of domestic violence, access to a gun, had previously made threats, and had poor mental health or substance abuse issues.
Coleman urged people in potentially dangerous relationships, as well as those who might be aware of friends or family struggling with domestic violence, to reach out to authorities.
Reporting domestic violence
Victims of domestic violence, as well as friends and family who may see warning signs, are urged to call 800-897-LINK (5465) or visit udvc.org. Callers are allowed to remain anonymous.