The 16-year-old boy who died in U.S. custody April 30, days after crossing the southern border following a long and perilous trek from Guatemala "was a very nice student, intelligent, creative, but shy," according to a former teacher.

Juan de León Gutiérrez, a 16-year-old Guatemalan boy who died in U.S. custody on April 30. CBS News

Juan de León Gutiérrez's former elementary school teacher described him as a hardworking boy who helped his father in the region's dwindling coffee fields, where drought and decreasing prices have led to debt and unemployment. Ultimately, the boy followed the recent path of as many as 30 youths from his small southeastern Guatemalan village, heading north toward the United States.

"Juanito was a very humble child full of dreams, dreams that vanished in a country other than his," teacher Jimmy Cristian Gutiérrez García said in an interview with CBS News. "Today we mourn his death."

"He was very cheerful and responsible in his studies and chores," said García, who provided CBS News with a photo of the two of them standing side by side, García handing Gutiérrez a diploma. "There was always a smile and a greeting for his classmates and teachers."

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Gutiérrez was apprehended by border patrol agents near El Paso on April 19 and transported the next evening to Casa Padre, a shelter for unaccompanied migrant children in Brownsville, Texas. When he awoke on April 21, staff noticed he appeared ill, and nine days later he died in a hospital bed. The Guatemalan Foreign Ministry said in a statement that Gutiérrez died from complications from an infection in his brain's frontal lobe.

Juan de León Gutiérrez (left) a 16-year-old Guatemalan boy who died in U.S. custody on April 30, and his former teacher Jimmy Cristian Gutiérrez García (right). Jimmy Cristian Gutiérrez García

Gutiérrez was the third migrant child to die in U.S. custody since December. Seven-year-old Jackeline Caal died in the custody of U.S. Customs and Border Protection on Dec. 8, 2018, after going days without food and water. Eight-year-old Felipe Gomez Alonzo died on Dec. 24, 2018, in border patrol custody after developing the flu.

All three children were from Guatemala, a Central American country where economic hardship, crime and corruption have sent increasing numbers northward seeking opportunity and safety. A survey of more than 1,500 people published May 2 in the Guatemalan newspaper Prensa Libre found that as many as 39 percent of the country's residents have contemplated migrating.

García recalled with sadness that Gutiérrez was a very motivated kid who "demonstrated ability in many things."

García said when the boy missed class he would run out to the road as García walked by to explain his absence—it was typically because his father needed help in the fields.