BANGOR — A Maine man charged with killing his girlfriend and her two young children at their home in Garland told investigators that he chased down and strangled the 10-year-old boy and 8-year-old girl because they had witnessed their mother’s death, according to court records released Monday.

The details are contained in an affidavit about the case against Keith Coleman, who faces three counts of murder in the deaths of Christina Sargent, 36, and her children, Duwayne Coke and Destiny Sargent. Coleman, 27, was ordered held without bail during a court appearance in Bangor.

The probable cause affidavit was filed by Greg P. Mitchell, a Maine State Police detective.

Investigators said the three bodies were found Saturday night in the mobile home Coleman shared with the victims at 12 Paul Road in Garland, a small town in Penobscot County.

A state medical examiner’s autopsy of the mother and children found all three were killed by “ligature strangulation,” said Timothy Feeley, a spokesman for the Maine Attorney General’s Office.

“Two of the deaths involved other forms of asphyxia as well,” Feeley said.

Court-appointed attorney Martha Harris represented Coleman during his appearance. She did not return messages seeking comment.

The affidavit said Andra Medina, an occasional resident of the mobile home and an aunt of Sargent, “had concerns about domestic violence problems” involving the couple.

Medina, who was at work in Bangor, attempted to contact Sargent 11 times on Saturday by phone and by texting her with no success, according to investigators.

Medina asked a cousin, Rebecca Ray of Ellsworth, to check on Sargent after being unable to contact her.

Ray and several other individuals who went to the home Saturday night to check on Sargent’s well-being discovered the bodies of Sargent and Destiny before calling 911.

Destiny was lying on her back with a cord around her neck and white plastic bag stuffed in her mouth. Duwayne had a USB cord wrapped around his neck. Sargent, who was wearing a bathrobe, was lying on her stomach with a pair of sweatpants wrapped around her neck, according to the police affidavit. The affidavit does not spell out a motive for the slayings, but a neighbor who was interviewed by police gave some clues about the relationship between Sargent and Coleman.

Natasha Geisinger, who lives at 5 Paul Road, said that Sargent came to her home last Thursday in tears. Geisinger told police that Sargent told her she “was sick of being abused by Keith Coleman and his controlling her.”

According to the affidavit, Coleman admitted to the crimes, telling police he fled in a van to a friend’s home in Bucksport after killing Sargent and the two children.

Police took him into custody in Bucksport on Sunday afternoon and later conducted a series of interviews with him at the state police barracks in Bangor. Coleman was charged with three counts of murder around 9 p.m. Sunday.

During their questioning of Coleman, Mitchell and another state police detective, Thomas Pickering, said he told them he had “a physical altercation with Christina Sargent in their bedroom and that he killed Christina Sargent.”

In the affidavit, police said Duwayne and Destiny “were standing in the bedroom doorway and screaming at him as they witnessed him killing” their mother.

Coleman told police he decided to kill the children because they had witnessed the crime.

Ray told police in the affidavit that Coleman went by the nickname “KO” and is originally from New York. Family members told the Portland Press Herald that the couple had been living together in Garland since 2012.

The children attended Ridge View Community School in Dexter, where Duwayne was in the fourth grade and Destiny was in the third grade, according to Superintendent Kevin Jordan. He described the children as typical grade-schoolers who were “happy to come to school, happy to be here.”

“It’s unbelievable,” Jordan said. “I wonder where we’ve come to in this world when things like this happen.”

The triple homicide was similar to a June 2011 domestic violence triple homicide in neighboring Dexter, where 37-year-old Steven Lake shot and killed his wife, Amy Lake, 38, and their children, Coty, 13, and Monica, 12. The couple had been feuding and were in the process of getting a divorce.

Amy Lake taught kindergarten at Ridge View Community School. Coty and Monica Lake were enrolled as students at the school – the same school attended by Duwayne Coke and Destiny Sargent.

The Garland triple homicide brings to 12 the number of domestic violence-related slayings in Maine this year, according to Stephen McCausland, spokesman for the Maine Department of Public Safety. He said at least six of the victims have been children. He said there have been 19 homicides reported in Maine this year.

The school district will have social workers available on Tuesday and counseling available when students return from break on Jan. 5.