A man with a violent criminal history entered a Houston home through an unlocked window and fatally shot a woman he'd previously dated, her husband and six children, including a boy believed to be his own son, authorities said.

David Conley, 48, is charged with capital murder in the deaths and is set to make his first court appearance Monday morning before a trial judge. Conley, who is being held in the Harris County Jail and doesn't yet have an attorney, didn't appear at a court hearing Sunday at which he was denied bond.

The dead, who all shot in the head, were identified as parents Dewayne Jackson, 50; his wife, Valerie Jackson, 40; and their children Dewayne, 10; Honesty, 11; Caleb, 9; Trinity, 7; and Jonah, 6. Also killed was a 13-year-old, Nathaniel, who was believed to be Conley's son from the relationship with Valerie Jackson.

"We do not — cannot — fully comprehend the motivation of an individual that would take the lives of so many innocent people. Especially the lives of the young ones," said Chief Deputy Tim Cannon of the Harris County Sheriff's Office. "The killer's motives appear to be related to a dispute with Valerie, who was his former domestic partner."

Authorities were first alerted Saturday about a problem at the home when a relative of Valerie Jackson's contacted the sheriff's office to request a welfare check.

"Upon arrival, deputies made multiple attempts to establish contact with residents inside the home. No contact was made," Cannon said.

After authorities learned that Conley, who had once lived in the home, had a warrant for his arrest for an assault charge, the sheriff's office High Risk Operations Unit was called.

"While awaiting response for the (unit), the body of an unidentified child was observed through a window at the residence," he said. "Deputies on scene forced entry into the home and were immediately met with gunfire. The deputies withdrew from the home ... and awaited the arrival of the" unit.

A standoff ensued for several hours between Conley and authorities until Conley surrendered, said Sgt. Craig Clopton, the lead investigator.

Investigators declined to say when on Saturday the victims were shot or if any victims were alive when deputies first tried to enter the home.

According to an arrest affidavit, Conley told authorities that he discovered on Saturday morning that the locks had been changed at the home after he had moved out. He entered the home through an unlocked window, the affidavit said.

According to Clopton, Jackson and Conley had a relationship, which ended, and "then (Dewayne Jackson) began a relationship with Valerie, which led to five children."

That relationship ended and Conley and Valerie Jackson began another relationship, before breaking up again, Clopton said.

Court records show Conley's criminal history dates back to at least 1988, with the most recent incident last month, when he was charged with assault after allegedly assaulting Valerie Jackson. The attack happened at the home where the bodies were found.

Conley pushed Valerie Jackson's head against a refrigerator multiple times after she tried to stop him from disciplining her son with a belt, the documents alleged. The case was still pending.

In 2013, Conley was charged with aggravated assault for threatening Jackson with a knife. He pleaded guilty and was sentenced to nine months in the county jail.

In 2000, he was sentenced to five years in prison for retaliating against his then-girlfriend after she had filed an assault charge against him. It was unclear if that woman was Valerie Jackson.

Authorities declined to comment on assault charges Conley had faced in the past or what prompted relatives to worry and request that deputies be sent to the home on Saturday.

___

Follow Juan A. Lozano on Twitter at www.twitter.com/juanlozano70