Earlier in the day, del Rosario's close friend, flyweight fighter Ian McCall,
Del Rosario suffered a heart attack on Nov. 26 in his home in Newport Beach. His manager, Jason House, said several days later that doctors suspected del Rosario had a genetic condition called Long QT Syndrome.
According to Yahoo Health, LQTS is "a heart rhythm disorder that can potentially cause fast, chaotic heartbeats. These rapid heartbeats may trigger a sudden fainting spell or seizure. In some cases, your heart may beat erratically for so long that it can cause sudden death."
An official cause of death has not been released.
Del Rosario was 11-2 in his MMA career, finishing it with a pair of losses in the UFC. He was scheduled to fight Guto Inocente on December 28 at UFC 168, but had to pull out of the match because of a rib injury.
His career was interrupted in 2011 when he was seriously injured in an auto accident when he was hit by a drunk driver. That kept him out of action for more than a year.
A graduate of the University of California-Irvine, he was known by friends as a compassionate, caring man who went out of his way to help others. In a 2012 video interview with Fight Magazine, del Rosario spoke of his desire to use his fight career to do good works for others.
"I have this rare opportunity that a lot of people don't have, to fight in front of thousands for the UFC and really make a name for myself and use that as momentum to help others. For me, I feel like I'm in position that, not only can I help myself to be a successful fighter, but if I do that, I can help a lot of other people after the fact."
In its statement announcing his death, the UFC said:
"The Ultimate Fighting Championship mourns the tragic loss of heavyweight competitor Shane Del Rosario, who has passed away at the age of 30. Del Rosario suffered a heart attack on Tuesday, November 26 as a result of what doctors believe to a congenital heart disorder, according to his manager Jason House.
"The entire organisation sends its deepest condolences to Shane's family and friends."
Services are pending.