A U.S. Army veteran who served two tours of duty in Afghanistan was deported to Mexico after his application for citizenship was denied because of a felony drug conviction, his lawyer and immigration officials said.

Miguel Perez-Montes, 39, was flown on Friday from Gary, Indiana, to Brownsville, Texas, where he was escorted across the border to Mexico, Nicole Alberico, an Immigration and Customs Enforcement spokeswoman, said in a statement.

Perez-Montes, who came to the United States legally when he was 8 years old, was convicted in 2010 for delivering cocaine to an undercover officer, a felony drug charge, and sentenced to 15 years in prison. He was placed into removal proceedings in 2012, while behind bars in Illinois, and had been in ICE custody since Sept. 23, 2016, Alberico said.

Perez-Montes’ case rose to prominence after Sen. Tammy Duckworth, D-Ill., an Iraq War veteran, appealed to the Department of Homeland Security on Friday to stay his deportation and review his case.

“This is a deplorable way to treat a veteran who risked his life in combat for our nation,” she wrote in a letter to the secretary of homeland security, Kirstjen Nielsen.

Perez-Montes enlisted in the Army in 2001, before the Sept. 11 terror attacks. As a paratrooper and private first class in Afghanistan in 2002 and 2003, he began suffering from “severe” symptoms of post-traumatic stress disorder, Duckworth said. He was discharged in 2004.

Seven years later, in 2011, the Department of Veterans Affairs diagnosed him with PTSD related to his service, the senator said. “Without proper V.A. care, he self-medicated with drugs and alcohol to cope with his PTSD, which eventually resulted in his drug conviction,” she added.

Asked about Duckworth’s letter, the Department of Homeland Security said today that its Citizenship and Immigration Services division had denied Perez-Montes’ request for naturalization on March 15 because of the felony conviction.

“After his two tours of duty with the special forces, he came back a broken man due to the horrors he witnessed in Afghanistan and the physical brain injury he suffered while there,” said Christopher Bergin, Perez-Montes’ lawyer.

He said Perez-Montes’ role was to repair vehicles in Kandahar, and that his brain injury occurred after a grenade went off near his vehicle.

Perez-Montes’ family was not alerted before he was deported, Bergin said.

“His family was never able to hand him some money and some clothes before they deported him in his prison clothes,” Bergin said. “He had nothing else.”

Perez-Montes lived in Mexico until he was 8, when he came to the United States on a petition through a family member. He was raised in Chicago and has been a permanent legal resident since age 11, according to a statement on Duckworth’s website. He was never in the country illegally, Bergin said.

Bergin said that Perez-Montes, who has two children who are citizens, was afraid that if he returned to Mexico he would become a target of cartels that would try to recruit him because of his military experience, or kill him if he refused. Bergin said last week that he planned to appeal the denial of citizenship “as far up the court ladder as we must climb.”