Fullerton was last seen in Braggadocio, Missouri on June 25, 2020. His girlfriend stated he walked away from her residence while she was in the bathroom, and she thought he might be headed to his grandfather's house two miles away. He never arrived there. He left behind all his belongings. His cross necklace, which he never removed, was found broken on the floor of his girlfriend's home. It’s uncharacteristic of him to be out of touch with his family. All of Marc's teeth have been extracted. He had a full set of dentures but wasn't wearing them when he disappeared. His ears are pierced and he has a scar on the knuckles of his right hand. Marc has extensive black and gray tattoos, including his name "MARC" in Old English script on his abdomen just above his navel, full sleeves of a skull-themed design on both arms, and the names "Aiden" and "Cade" across his upper chest just below his collarbone. He had a goatee at the time of his disappearance. He wore eyeglasses, but left those behind.