Steve Mostyn, a top Democratic donor and prominent Houston trial lawyer, has died. He was 46.

According to a statement released by his wife, Amber, Mostyn died Wednesday after "a sudden onset and battle with a mental health issue." She did not disclose the cause of death.

"Steve was a beloved husband and devoted father who adored his children and never missed any of their sporting activities. He was a true friend, and a faithful fighter for those who did not have a voice," she said.

The statement also said: "If you or a loved one are thinking about suicide, or experiencing a health crisis, call the National Suicide Prevention Lifeline right now at 1-800-273-8255."

Mostyn is also survived by his daughter, Ava, his son, Mitch and his nephew, Skyler Anderson.

Mostyn grew up in Whitehouse, a small town in East Texas, and graduated from the South Texas College of Law. He made his fortune suing insurance companies on behalf of homeowners after hurricanes. He and his wife, also an attorney, have long been considered the state’s most powerful Democratic backers, spending millions on Democratic campaigns in Texas and beyond.

But Mostyn didn’t just spend money behind the scenes. He often made his opposition to Republican leaders and policies known in plain and public terms. In 2010, he famously paid for full-page ads in Texas newspapers calling Gov. Rick Perry a “coward” for refusing to debate his Democratic rival, former Houston Mayor Bill White.

“Steve was a giant," Texas Democratic Party Chairman Gilberto Hinojosa said in a statement. "He was the epitome of a Texas Democrat – big, bold, fearless, and caring. He dedicated his professional and personal life to fighting for the little guy."

Mostyn gave more than $2.3 million toward Democrats' 2014 efforts to elect candidates including Wendy Davis, who ran for governor. In total, he had given Davis more than $3 million over the course of her political career. Since 2000, he had donated more than $24 million to political causes in his name and in his law firm's name, according to Texas Ethics Commission records.

"I am heartbroken," Davis tweeted Thursday. "Texas has lost an extraordinary person. Steve was a committed and effective fighter for justice, a wonderful husband, father and friend. He leaves behind a lasting impact on everyone who’s life he touched."

The Mostyns were among the top contributors to former state Sen. Leticia Van de Putte's failed 2014 run for lieutenant governor, giving her campaign more than $100,000.

“Mine is just shock,” Van de Putte said tearfully Thursday. “He was a very dear friend. He loved his state and he loved his kids. ... He felt fervently about Democratic candidates and politics. He will leave a void that will be very difficult to fill,” she said.

U.S. House Minority Leader Nancy Pelosi called Mostyn "an extraordinary, luminous person who poured himself into securing justice for the voiceless and underrepresented."

“Our nation has lost a great hero, and the Mostyn family has lost a beloved husband and devoted father," Pelosi said in a statement.

In Amber Mostyn's statement, she asked those wishing to honor her husband's life to consider supporting the Mostyn Moreno Foundation, which helps children with special needs, or the Special Olympics of Texas.

The Texas Tribune interviewed Mostyn in mid-September right after Hurricane Harvey struck Houston. Mostyn made it clear he was taking a wait-and-see approach on any Harvey-related lawsuits.

He was far more effusive about his other passion — politics.

Toward the end of the interview, Mostyn candidly spoke of his increasingly diminished role as a Democratic mega-donor. He said he was growing tired of almost single-handedly funding top Democratic candidates in a state hostile to their party.

Asked why no major Democratic candidate for governor had yet emerged, Mostyn said “the problem is if we go and ask someone to run for governor then they expect us to fund them with a tremendous amount of money, and you’re talking about a state that has 20-plus media markets, right? I mean it’s an expensive proposition to do.”

“You know we’ll be there to do our part, for sure, and other folks have got to step up to do their part,” Mostyn told the Tribune. “People say I’m not here to do the politics, and I say we’re slowing down on a lot of things. We’re just a little bit slowing down. We were running pretty hard for 20, 25 years.”

Mostyn said he had deliberately decreased his political activities in part to encourage other Democratic donors to open their wallets.

“We’ve lowered our head down because a lot of times what’s happened is people just think we’re going to do it,” Mostyn said. “And so we’ve asked other people to do it, and they want to do it, and I want other people to get credit for doing it. I mean this is a giant, giant state. If we were trying to flip Vermont, we’d be done."

Mostyn seemed wistful when he talked about his desire to spend more time with his children and enjoy the simpler side of life.

“I want to go watch Friday night football with my son and go to my little girl’s swim meets and I want to do all those things,” Mostyn said. “I’ve got a nephew we raised who’s 19 and he’s off at college, and I’ve got a 16-year-old and I’ve got a 10-year-old. And we’re at the point where, you’re running, running, running, and you look up one day and you say, 'We’re doing fine, but are we really enjoying the things we want to be enjoying?' I’m not saying I’m going away anywhere, but we’ve formed these groups and we’re on these boards and certainly we’re there participating with them, but we’ve asked people to — you know, guys, you’ve got to build a broader coalition.”

Disclosure: Steve Mostyn was a financial supporter of The Texas Tribune. A complete list of Tribune donors and sponsors is available here.

Additional reporting by Ryan Murphy and Alana Rocha.