According to the county of Delaware, Pennsylvania autopsy report obtained by RadarOnline.com, Cotton, 32, suffered a blood clot in his lungs that caused his heart to give out.
"I conclude the cause of death was due to pulmonary thromboembolism, right lung complicated by cardiomegaly," the medical examiner wrote. The term "cardiomegaly" refers to an enlarged heart.
"Significant conditions contributing to death is morbid obesity," the examiner added.
His sister-in-law, Karen Middleton, told RadarOnline.com that Cotton was discovered by a close friend in his vehicle "slumped over."
Cotton was then transferred to the hospital but passed away at 1:30 PM on Wednesday, December 11.
"We are all just shocked that this happened," Middleton said. "He was just going to the store to get some stuff for the baby too."
As RadarOnline.com readers know, Cotton was expecting his first child in February with wife of eight years, Erica.
The Philadelphia stand-up comedian regularly appeared on Comedy Central and was the cohost of Every Damn Day.
"We're devastated by the loss of Chris Cotton – a hilarious comedian, a beloved member of the Comedy Central family and a joy to be around," Comedy Central said in a tweet. "He will be missed."
In July 2018, he was the red carpet host for the network's Bruce Willis roast. Prior to that, he appeared in Carpool Rules, a 2015 web series.
An evening of comedy in Cotton's memory is planned for January 6 at the Loft at City Winery in Philadelphia. Memorial services in Philadelphia and New York will be announced.
A GoFundMe page has been set up to help support Cotton's family.