SALT LAKE CITY >> A Utah man killed his girlfriend and her 3-year-old son, then wrapped their bodies in sheets and dumped them in a remote part of the state before they were reported missing two years ago, prosecutors said in charges unsealed Monday.

Emily Almiron, 23, and her son, Gabriel, have never been found, but authorities have filed aggravated murder charges against her then- boyfriend. Christopher Richard Poulson, 28, was arrested over the weekend near Dole Plantation on Oahu, where he moved shortly after being confronted with evidence collected over two years of investigation by Orem police and the FBI, prosecutors said.

Police say a cadaver dog detected the presence of human remains in the trunk of a Mustang that Poulson sold cheaply shortly after Almiron and her son vanished on Sept. 8, 2015. A roommate later told police a hammer disappeared around the same time Almiron went missing, charging documents state.

Authorities also cite records showing Poulson drove to trash bins near their apartment in Orem, about 40 miles south of Salt Lake City, the day after they disappeared, according to GPS data in charging documents. He then bought a shovel and work gloves and drove to a rural area, according to the charges.

The following day, he bought sheets and another pair of gloves before leaving Almiron’s Toyota Prius filled with bags of her things and the boy’s car seat in a parking lot in the southern Utah city of St. George.

Poulson has told police he broke up with Almiron because he found drug paraphernalia in their apartment, and she left with her son, according to charging documents. Prosecutors, though, say Poulson used drugs, including both marijuana and methamphetamine, himself.

No attorney or publicly listed phone number was available for Poulson on Monday.

He later moved to the northern Utah town of Smithfield and told friends Almiron had moved to California, charges state. But police searched driver’s license databases all over the country without finding her. They also say she would be unlikely to leave shortly before she was due to graduate from a massage therapy school where she had paid $13,000 in tuition. Her credit cards and phone have gone unused since Sept. 8.

The aggravated murder charges carry the possibility of the death penalty, though prosecutors haven’t yet said whether they will seek it.

Star-Advertiser writer Nina Wu contributed to this report.