The gun has not been recovered and the suspect in those murders remains at large.
Douglass Watts and Eliyahu Moscowitz died just 36 hours apart. Watts, 73, was shot "execution style" while walking his dog in the 1400-block of Sherwin Avenue on Sept. 30. Moscowitz, 24, was shot in the head on the Loyola Park path near Lunt Avenue on the evening of Oct. 1.
WATCH: Surveillance video of Rogers Park murder suspect
"The shell casings found at both crime scenes from the 1100-block of West Lunt and the 1400-block of West Sherwin Avenue from Sunday were found to be a match," Police Superintendent Eddie Johnson said at the time. "This means both shootings came from the same gun and likely the same suspect."
Police released surveillance video of the suspect, which they believe was taken moments after Watts was murdered.