Attorney Brian Loncar, known for his TV moniker "The Strong Arm," died last month due to an accidental cocaine overdose, officials said Thursday.

Loncar's death was primarily due to the toxic effects of cocaine, but a secondary factor was hypertensive and atherosclerotic heart disease, according to the Dallas County medical examiner's office.

The personal injury lawyer, 56, was found dead in his new Rolls-Royce Wraith on Dec. 4, days after burying his youngest daughter, Grace Loncar, who had killed herself at age 16.

Grace Loncar

Brian Loncar had long struggled with drug and alcohol addiction, as well as bipolar disorder and depression, according to those close to him. His family was devastated to hear he died of cocaine use but not entirely shocked, said his stepson, David Long, 32. Long was raised by Loncar since childhood and considered him a father.

"I wouldn't say we were shocked, but we were definitely surprised," Long said in a written message. "We knew that Brian struggled with not drinking the last several years and that he was doing cocaine a couple years ago for a little bit, but we did not know that he had been doing it recently."

Loncar had been sober for about 20 years until a few years ago, Long said. He nearly died in a crash with a Dallas firetruck in 2008 and was prescribed pain medication. The wreck deeply affected him, Long said.

"Honestly, Brian was never the same after his near-death accident with the firetruck," Long said. "He struggled a lot after that and was almost a different person."

The Loncar family also released a statement, saying, "While we accept this scientific finding, those of us who were closest to him already knew the cause of his death. Brian died of a broken heart.

"These are unimaginable losses for our family. Hopefully, these events will serve as heartbreaking reminders that we all need to reach out and care for our loved ones — every day."

Loncar was the one who found his daughter's body, the family said. In the days after, he told his wife, Sue, that he wasn't sure he could keep living. Yet he also pledged to take time off from work and find a way for them to be happy again.

The Grace and Brian Loncar Foundation website.

Loncar found a sense of purpose in starting a foundation in Grace's name to help other families fight depression and prevent suicide. He spoke excitedly to friends about the cause — no one thought it would soon become the Grace and Brian Loncar Foundation.

The Loncars had long dealt with mental health issues. Grace, a talented actress and singer at Booker T. Washington High School for the Performing and Visual Arts, had battled depression since age 11.