On July 26, John Kenneth “Ken” Dunn, the co-founder of Dallas real estate firm The Rainier Companies, died in a tragic airplane crash.

The plane crashed in the late afternoon at the Truckee Tahoe Airport in northern California, according to the Federal Aviation Administration (FAA). The crash claimed the lives of six victims including Dunn, The Sacramento Bee reported.

“The Rainier family is deeply saddened by the loss of its co-founder, partner and friend,” Rainier President and CEO Danny Lovell said in a statement, according to the Fort Worth Star-Telegram. “Our most heartfelt sympathies go to Ken’s family during this unbelievably difficult time. He will be terribly missed.”

Dunn originally co-founded Rainier Capital Management with Tim Nichols in 2003, Fort Worth Star-Telegram reported. The firm has closed over $2.5 billion in investment assets. 

“Ken loved to engage people, make them laugh and bring them into his orbit for both business and personal friendship,” the statement said.

Dunn is survived by his wife, son, daughter, stepdaughter, stepson, three grandchildren, his mother, brother and sister, according to CBS DFW News.

The cause of the plane crash is currently unknown and is still under investigation by the Truckee Police Department, the FAA and the National Transportation Safety Board (NTSB).

The Sacramento Bee reports that the plane was traveling from the Coeur D’Alene Airport in Idaho to Thermal in Riverside County before heading to Van Nuys Airport in Los Angeles.