Police said the man, identified as Ljubisa B., allegedly shot and killed six women, six men and a 2-year-old boy, all "neighbors and relatives," B92 reported
After the spree, the man tried to kill his wife and then commit suicide, police said. Both survived and were in critical condition.
Serbian Police Director Milorad Veljovic said 12 victims died immediately and the 13th victim died en route to the hospital.
Veljovic said no motive had been determined. Reports indicated the suspect used a CZ88 pistol for which he had a permit.
"This affected five homes, relatives and neighbors," Veljovic said. "At this moment we have nobody to talk to ... because five houses have been effectively shut down."
One neighbor told B92 the suspect was a non-violent man who "never created any problems."
The neighbor said the suspect was behaving normally Monday, "and then something cracked in his head during the night."