Wilson Barajas vanished last Saturday after he left his home on the city's Southwest Side.
Relatives say he told them he was going for a walk at McKinley Park just a few blocks away. But the 30-year-old never returned home. They says it's unusual for Barajas to ignore his mother's phone calls.
"She gave him a call and he never answered so that really was suspicious...he just didn't answer her," said Aracely Barajas, cousin.
Family members say Barajas had been suffering from fatigue and nausea for several days before he disappeared.
Barajas graduated with two masters degrees from UIC earlier this month.