DENVER (KDVR) — The partner of a 28-year-old mother of four found dead on an Amtrak train in 2016 has been arrested.

Angelo Valentino Mantych, 41, is being charged with first-degree murder in the death of his partner, Marina Placensia.

According to an affidavit acquired by the Problem Solvers, detectives responded to Union Station on the morning of Sept. 1, 2016.

They found Placensia dead on the train. She had reportedly boarded a train in Wisconsin with Mantych and their four children the day before and then switched to a different train with them after a stop in Chicago.

Mugshot of Angelo Mantych
Mugshot of Angelo Mantych, who is charged with the first-degree murder of Marina Placensia (Credit: Denver District Attorney’s Office)

“I want to thank the prosecutors and investigators in my office, as well as the detectives with the Denver Police Department, whose work on this case has gotten us to this point.  I also want to thank the Racine (Wisconsin) Police Department and the Amtrak Police Department for their invaluable assistance with the investigation,” Denver District Attorney Beth McCann said in an email about the arrest.

She was found unresponsive on the train prior to it arriving in Denver. An autopsy said there were 35 injuries to her body, mostly caused by blunt force trauma.

Marina Placensia died on a train bound for Denver in 2016. Seven years later, in 2023. her partner was charged with her murder.
Marina Placensia died on a train bound for Denver in 2016. Seven years later, in 2023, her partner was charged with her murder.

Initially, her death was ruled undetermined. However, according to the affidavit, the investigation continued.

In September 2023, a nationally recognized expert in strangulation and suffocation who had agreed to review the case a year prior issued a report and said he believed Placensia died of suffocation.

The expert Dr. Bill Smock said in his report that the manner of death was homicide.

Previous coverage

In 2017, the Problem Solvers interviewed many people in Placencia’s life who alleged Mantych physically abused her for years.

Her family also said they had come up with a plan in August 2016 where Placensia would come to Denver and, once in the safety of her mother’s house, file a restraining order and seek a divorce.

Her brother said she was ready to “break the cycle” and leave Mantych.

“That’s why I was [at Union Station]. To let him know she’s not going home with you. She’s coming home with us where she belongs,” he said in 2017. “We were going to take care of those kids and take care of her.”