An Army Reserve member drowned in a Texas lake Saturday as he tried to save his fiancee's 6-year-old daughter, The Dallas Morning News reported.

Brandyn Mitchell, 25, dove into Lake Ray Roberts near the north Texas city of Denton to help Keira Herrera get back onto a flotation device, the Fort Worth Star-Telegram reported.

"He was already on the float with (Keira) when she was struggling to hang on," Mitchell’s fiancee, Angelia Herrera, told the Star-Telegram. "He helped her, told her not to let go, then slipped."

Game Warden Darla Barr told the Denton Record-Chronicle that after the child made it to shore, bystanders could not find Mitchell.

Three hours later, rescuers with the Lewisville Fire Department's dive team pulled Mitchell’s body from water that was about 6 feet deep, the Morning News reported.

Mitchell's heroic act at the lake was typical of his character, Herrera told the Star-Telegram.

"He was in the process of enrolling in college to become a firefighter. He wanted to be a firefighter because he wanted to save lives. Running in when everyone is running out. He wanted to be a hero, not just once but every chance he could," Herrera told the newspaper. "Shortly put, he was an amazing man and I am lucky to have known him."

Mitchell’s mother, Stacy Thompson, said she was puzzled that her son drowned.

"Being in the Army and all that, he could swim like a fish. That's why I can't understand what happened," Thompson told the Star-Telegram.

Herrera said she and Mitchell had set a wedding date before heading to the park, the Star-Telegram reported. They had one child together, 1-year-old Bryson, and were planning to combine families with Keira and Mitchell’s two children, Paris and Trenton Mitchell, the Star-Telegram reported.

Mitchell’s Instagram profile included the hashtags #proudfather and #soldier, and his Facebook page focused on his love for the Dallas Cowboys and snakes, the Morning News reported.

"He was an amazing father," Herrera told the Star-Telegram. "He was loved and will be missed. No matter what, he was a hero."