Dallas lawyer Brian Loncar died Sunday, two days after the funeral for his 16-year-old daughter, who killed herself Nov. 26.

Police found Loncar, 56, unresponsive about 9:45 a.m. in the front seat of his new Rolls-Royce Wraith, which was parked outside the downtown office of his law firm, Loncar & Associates, in the 400 block of South Cesar Chavez Boulevard.

He was taken to Baylor University Medical Center, where he was declared dead.

The cause and manner of his death are still under investigation. Police say a routine toxicology test will be conducted by the Dallas County medical examiner's office, which may take several weeks to release.

Stepson David Long said that a team at Baylor had notified the family that Loncar's death was probably caused by a heart attack. Neither Baylor officials nor the medical examiner's office could confirm that.

"Our family is filled with enormous sadness and profound grief," Loncar's family said in a statement Sunday. "Right now, we are hurting and struggling to understand. Today, we are embracing each other; we know this pain and heartache will be with us forever."

The prominent personal-injury lawyer made a name for himself as the "Strong Arm," a moniker that became a household phrase thanks to a series of TV ads that he starred in.

The commercials featured a bicep and forearm pounding against steel and Loncar promising to get clients the money they deserved if they were injured in a car accident.

His firm had offices in 11 cities across Texas and employed almost 20 lawyers.

In a statement Sunday evening, the firm said Loncar's colleagues were shocked by his death.

"We are remembering and honoring his passion, commitment to his clients and skillful representation of people who are in pain and need the firm's assistance," it said in a Facebook post.

Loncar made headlines in May 2008 when he was seriously injured in a collision with a Dallas Fire-Rescue truck.

The truck, on its way to an emergency, smashed into the driver's side of his 2008 Bentley in Oak Lawn, breaking his pelvis and 10 ribs and collapsing one of his lungs.

Grace Loncar

Tragedy struck again for the family last month, when Loncar's youngest daughter, Grace, killed herself after a long battle with depression, according to her obituary.

She was a junior at Booker T. Washington High School for the Performing and Visual Arts, where she won awards for acting.

Loncar posted an emotional message Saturday morning on Facebook about Grace's death and her memorial service, which he said was attended by 1,000 people.

"She told me she could never feel love," Loncar wrote. "I just want to get this out in the open so if any of my friends are ever thinking about suicide. I wish you could have seen both the pain and love that the suicide of a 16-year-old girl causes."

Loncar is survived by his wife, Sue, who is the artistic director of the Contemporary Theatre of Dallas; five children, David, Patrick, Sally, Hailey and Abby; and his parents, Sue and Phil Loncar.

Staff writers Naomi Martin, Nancy Churnin and Tom Steele contributed to this report.