Oliver Jack Carter Lomas-Davis, who quickly became famous on social media, died on Feb. 25 of Sudden Infant Death Syndrome, PEOPLE reported on Thursday, citing a Facebook post from his mother.
"I love you dearly, I love you most. I love you with all my heart and soul. I know that God will keep you near since God and truth are here," Souxsie Lomas wrote in the post on Facebook.
Wearing a white wig and a "Bernie 2016" button, Oliver met Sanders at a rally in Las Vegas on Feb. 14.
Family members have set up a GoFundMe page to help pay for the cost of his funeral service and burial. As of Thursday, the page had raised more than $17,500.