Lawyer Stephen Barnes who founded Cellino & Barnes and his attorney niece are killed in plane crash while flying to his mother's birthday party in New York

Lawyer Stephen Barnes of personal injury law firm Cellino & Barnes has been killed in a plane crash alongside his niece, Elizabeth.

Authorities confirmed two people died Friday when the single-engine Socata TBM-700, crashed about 11:45 a.m. in a wooded area near Pembroke, New York.

The aircraft was registered to a corporation that shares an address with Cellino & Barnes, which has offices in New York and California and is known for its catchy TV jingle.

'It is with great sadness that I learned of the tragic passing of Steve Barnes in a plane crash,' his longtime business partner Ross Cellino said in a statement to People.

'He was always a fearless advocate for his clients. His passing is a significant loss for the legal community.' 

Cellino & Barnes began as small firm in Buffalo but became well known in New York City and beyond for its ubiquitous advertising on billboards and on television. Pictured: Steve Barnes

Barnes' niece, Elizabeth, 32, who was also a lawyer at the firm died in the crash alongside him

Elizabeth Barnes was traveling with her uncle to her grandmother's birthday party. At the time of her death, Barnes was working as an assistant regional counsel at the U.S. Department of Health and Human Services in Boston

A helicopter circles the site of a small plane crash near Pembroke N.Y., Friday, October 2

Authorities confirmed two people died Friday when the single-engine Socata TBM-700, crashed about 11:45 a.m. in a wooded area near Pembroke, New York

'Equally heartbreaking is the passing of Elizabeth Barnes, sister of Brian Barnes and daughter of Rich Barnes, Steve's brother and an attorney at our firm.' 

Cellino told PEOPLE that Barnes' greatest accomplishment was his children Josiah, Rachel and Julia.

At the time of her death, Elizabeth Barnes was working as an assistant regional counsel at the U.S. Department of Health and Human Services in Boston.  

The pair were on their way to a birthday party in Buffalo for Barnes' mother when the plane crashed.  

Two sources told The Buffalo News that Barnes owned the plane.  

Neighbors described the plane making a loud, whining noise, then dropping into a wooded area, Sheron said.

'The airplane pretty much disintegrated,' Genesee County Sheriff William Sheron told reporters during a press briefing. 'There's not much left at all.'

Barnes was a registered pilot and before becoming an attorney was an officer in the  Marine Corps. He was a combat veteran of the Gulf War.

Cellino & Barnes old-time jingle, in which the law firm's phone number was put to song, has been the subject of a sketch on Saturday Night Live, and other late-night TV host jokes for years. 

The pair decided to partner with one another in 1992 and worked together for almost 30 years.

Eventually, Cellino filed to dissolve the firm in May 2017 after a number of built-up tensions and disagreements. 

Neighbors described the plane making a loud, whining noise, then dropping into a wooded area

Such were the disparities it took a further three years before the terms of their split was agreed, this June, according to the New York Post.

After the split, Barnes formed his own law firm, The Barnes Firm Injury Attorneys. 

The site states that accidents including drink driving, wrongful deaths and airplane accidents is the firm's speciality.   

Broadway actors in 2018 posted viral videos of themselves singing the jingle in what was dubbed the 'Cellino & Barnes Challenge.'

The law firm's principal lawyers, Ross Cellino and Stephen Barnes, who appeared together in the advertisements, had a falling out in recent years and battled each other in court.

The National Transportation Safety Board said it was investigating the cause of the crash. 

NTSB spokesman Terry Williams said the agency would release its initial report within seven to 10 days.

Cellino & Barnes old-time jingle, in which the law firm's phone number was put to song, has been the subject of a sketch on Saturday Night Live, and other late-night TV host jokes for years