A 41-year-old man is charged with murdering his girlfriend on an Amtrak train that was traveling from Wisconsin to Colorado in 2016, according to the Denver District Attorney’s Office.

The seven-year investigation began on Sept. 1, 2016, when Denver Police Department detectives responded to Union Station at about 8:15 a.m. to reports of a dead woman on board the train.

Marina Placensia, 28, was traveling from Wisconsin to Denver with her four children and boyfriend, Angelo Mantych, to move to Colorado.

Mantych told investigators he had been unable to wake his girlfriend from sleep shortly before the train arrived at the station and then went to get help.

But Placensia had visible injuries on multiple parts of her body, and an autopsy report found she had 35 internal and external injuries, including bruises on her face, scalp, chest, arms, wrist, hand, stomach and legs; rib fractures; and internal bleeding, according to an arrest affidavit.

Placensia’s death was initially ruled inconclusive because her injuries were not sufficient to explain her death.

Investigators continued to conduct interviews with friends, neighbors and family members, who reported Mantych abused Placensia almost daily and suspected he also abused their children.

In September, the Denver District Attorney’s Office received a report from a physician with expertise in asphyxia deaths who confirmed Placensia died as a result of being suffocated and that her death was a homicide.

Mantych was booked into the Downtown Detention Center on Monday, according to jail records.

Editor’s note: Due to a reporting error, this story previously identified Marina Placensia as Angelo Mantych’s wife. She was his girlfriend.

Sign up to get crime news sent straight to your inbox each day.