Chris LeCompte, 33, an off-duty Evergreen Park police officer, said he went down to Northwestern Memorial Hospital's cafeteria while his wife and newborn prepared to go home from the facility about 1:30 p.m. Monday when he saw two men "wrestling" on the ground, the Chicago Tribune reported Wednesday.
LeCompte said he attempted to break up the fight and one of the men attacked him.
"He tried to scratch on me and punch me," LeCompte said.
The new father said he was able to hold the man until security officers arrived.
Cook County State's Attorney's Office spokeswoman Lisa Gordon said the man captured by LeCompte was trying to get away after snatching a $600 iPhone from a pregnant woman in a wheelchair.
"The defendant walked by and took it and the victim told her husband who went after the defendant to get the phone back," Gordon said.
The suspect, Sean McBrady, 30, was charged with felony robbery and jailed in lieu of $150,000 bond.
"It was an exciting day, but it didn't need to be that exciting," LeCompte said.