EUGENE, Ore. (Reuters) - Anderson is obsessed with train videos.

His favorite shows the shadowy image of a steam engine - a “ghost train” - that seems to come out of nowhere. It reminds him of the freight trains he clung to during his 2,500-mile trek from southern Guatemala to the United States.

Anderson traveled - sometimes between swaying box cars or atop cargo pallets - with his maternal grandmother Blanca as part of the migrant caravan in spring 2018. He was 10 years old.

When Blanca, who helped raise Anderson, said they were going on vacation during his school spring break, he was excited. The first few days, he asked his grandmother, whom he calls Mama, why they had to walk so much on vacation. After two weeks, he began to worry about missing school.

Blanca, now 49, didn’t tell him she was running from her estranged husband, who she said had beaten and raped her and threatened to steal Anderson away. In Mexico City, she told Anderson they were headed to the United States to reunite with his mother, Wendy.

Reuters is not publishing the last names of Anderson and his relatives because he is a minor. Blanca’s allegations against her husband, which Wendy said Blanca related to her at the time, could not be independently confirmed.

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On the trains, Anderson suffered fevers, chills and motion sickness. He had to relieve himself in a plastic bottle. But it wasn’t all misery. Blanca recalled him looking up at the stars over the desert in northern Mexico, saying, “It’s beautiful, Mama.”

Two days after arriving at the U.S.-Mexico border, in May 2018, American officials placed Blanca in one room and Anderson in another.

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After Blanca said they feared returning to Guatemala - the first step toward an asylum claim - authorities sent them to separate detention facilities, Anderson’s in New York and Blanca’s in California. Such separations are common when an adult with a child is not the parent.

In New York, Anderson would spend his nights in foster care and his days at a shelter run by Cayuga Centers, which operates a network of facilities that hold young unaccompanied migrants on behalf of the federal government.

His troubles - described in case management records reviewed by Reuters and in interviews with Anderson and his mother - began almost immediately.

A boy pushed a table into his stomach, prompting Anderson to scratch the boy’s arm, according to an incident report. He scuffled with another boy over a pencil. He told social workers he missed his family. A psychiatric nurse diagnosed him with Attention Deficit Hyperactivity Disorder and put him on medication.

Anderson threatened a boy in foster care with a butter knife, telling a social worker later that he was upset the boy had kissed him on the lips.

Living in Eugene, Wendy, 28, said she was allowed only 10- to 15-minute calls twice a week with Anderson. She grew increasingly alarmed as the months passed.

In October, Anderson reported that three boys had choked and punched him, according to an incident report. Wendy showed Reuters a screenshot of marks on his neck that he displayed during a video chat with her.

In November, Anderson was diagnosed with scabies, an itchy rash commonly spread by skin contact in crowded conditions.

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Eight months into his detention, Anderson told counselors a boy had touched his private parts over his clothes, an allegation that was reported to New York child protective services and police, according to the case management files. Both agencies declined to comment. Wendy said police interviewed Anderson but dropped the case.

Richard Crompton, a spokesman for Cayuga Centers, said the organization could not comment on individual cases but that “all incidents which happen while a child is in our care are investigated” and all serious or sexual allegations are reported to the proper authorities for investigation.

The federal Office of Refugee Resettlement (ORR), which oversees migrant detention facilities, also declined to comment on individual cases. In a statement, the agency it said its mission, in part, is to provide a “safe and healthy environment.”

Anderson was detained as the Trump administration adopted complex vetting procedures for adult sponsors, creating a backlog that delayed kids’release. Some of those procedures have since been eased and Crompton said his centers now release most kids in less than a month.

Wendy sent desperate pleas for her son’s release, according to phone texts she shared with Reuters.

“Miss, please if you are a mother imagine yourself in my place,” Wendy wrote to one caseworker in December.

“If it were in my hands, believe me the child would have been with you a long time ago, but I am not the one making decisions,” the case worker responded.

In February, after nine months in custody, Anderson was released to his mother in Oregon. His grandmother Blanca was then in detention in Washington state.

“When everyone else is sleeping I pray that they will let my ‘Mama’ go,” Anderson told Reuters.

In August, Blanca was deported to Guatemala.

Anderson got one last visit, no touching allowed. “He put his hand on the glass and I put my hand up to his hand and he just cried,” Blanca said.