Photo: Family Photo

Alexia Rose Echeverria

A California man whose eight-month-old daughter was found dead one week earlier in her car seat behind a funeral home surrendered to the FBI on Monday at the U.S.-Mexico border.

“He was cooperative,” Sgt. James Wilcox, supervisor of the Sacramento County Sheriff’s Child Abuse Bureau, said at a Monday press conference. “He was not agitated.”

According to Wilcox, Echeverria faces charges “related to the death of his daughter.”

“We are still kind of working out through the details” of the charges, Wilcox said.

PEOPLE was not able to reach his attorney.

Echeverria’s daughter Alexia Rose was discovered May 27 behind a Bellflower funeral home — propped upright in a child’s car seat, partially covered with a blanket. Echeverria is from the Sacramento area and Bellflower is in Los Angeles County, more than 400 miles away.

National Center for Missing and Endangered

Alexander Echeverria

“Locating Alexander was a top priority for detectives given information that Alexia was in Alexander’s custody around the time of her death,” said Sacramento Sheriff’s spokesperson Tess Deterding at the press conference.

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Alexia Rose’s mother Karla Alvarado toldKTXL, “She was so perfect.” Alvarado added, “She was already calling me mama. She was clapping. I was trying to teach her how to crawl.”

Alexander and Alexia Rose Echeverria.National Center for Missing and Endangered

Alexia Rose Echeverria, Alexander Echeverria

Alvarado said Echeverria dropped her off at work in Sacramento on the morning of May 26. She said she saw her daughter for the last time one hour later when she FaceTimed with Echeverria, KTXL reports.

Alvarado told the station that Echeverria called his brother and “told him that he was playing with her, throwing her up [in the air], and he slipped and she fell, and she wasn’t waking up,” according to KTXL. “He said he got scared and he drove to the hospital but he never went in because he thought nobody was going to believe him that it was an accident.”

source: people.com