He is the 41st member of the military from Connecticut to die in Iraq or Afghanistan since the wars started. Two civilians from the state have also died.
Brown was due to take a leave and come home in about three weeks to spend time with his family and girlfriend, relatives said.
"He just called me three days ago and said he couldn't wait to get back," his twin brother, Timothy Brown, said Thursday. "He wanted to make a difference. The Army was lucky to have him."
After leaving Shelton, Thomas Brown graduated from George Mason University in 2004 with a degree in government and joined the Army in 2005. Timothy Brown said his brother went to Ranger school, Airborne school and officer's candidate school.
"He took every opportunity that came his way," Timothy Brown said.
Thomas Brown was a good moral person, his brother said. Everyone he met left with something from him, he said.
Funeral arrangements are pending.
Connecticut Gov. M. Jodi ordered that all U.S. and state flags in Connecticut be flown at half-staff in honor of Brown.
"We must never lose sight of the sacrifices our military members make each and every day as they serve our great country," Rell said in a statement. "We can best honor his selfless dedication to our freedoms by keeping Lieutenant Brown - and all our men and women overseas - in our thoughts and prayers."
