Ahmad Kahn Rahami’s terrorist inculcation likely occurred during two visits to a religious school in Pakistan in 2011 and 2013, a Pakistan security official told The Guardian.

The Afghanistan-born, U.S.-naturalized Rahami is said to have gone to the Kaan Nuwa Naqshbandi madrassa in Kuchlak, a major hub city for the Taliban. In 2011, he spent three weeks receiving “lectures and Islamic education,” the official said. He also spent nearly a year in Pakistan in 2013.

His father, who owns a fast-food restaurant in Elizabeth, New Jersey, told The Associated Press Friday that he recognized significant personality changes when his son returned from Afghanistan and Pakistan in 2013.

“His mind was not the same. He had become bad and I don’t know what caused it but I informed the FBI about it,” he said.

Rahami, 28, is believed to be the culprit behind the Chelsea bombing on Sept. 17 that injured as many as 31 people. He is also suspected of planting homemade bombs discovered around the same time on 27th Street in New York and in New Jersey. Fingerprints on the bombs, and his notebooks referring to terrorist icons, link him to the acts that appear to be Islamic-terrorism motivated, investigators said.

As for his education in bomb-making, it might not have been entirely from Internet instructions. A source told NBC he might have learned techniques such as how to make a “triggering-type device” in an electronics class at Union County College. He was enrolled in a few non-credit courses in 2008 at the community college, according to a spokesperson there.

Rhamai remains hospitalized and in critical condition following the Sept. 19 shootout in New Jersey that ended with his arrest.  He faces five-counts of attempted murder against the police he shot, and federal charges of terrorism. News media reports indicate he was not appointed a public defender and that attorney Peter Ligouri, contacted by his Rahami's father, was denied access to the suspect.