The source also told the Tribune the wife of a high-ranking police supervisor had been told in a phone call Monday her husband had been shot to death and the caller threatened the woman's life.
The supervisors' names and their star numbers appeared in Twitter postings during the summit, which ended Monday, a police source said. Chicago police clashed with protesters during the summit.
The source said a criminal investigation had begun but there was no evidence the department's Web site had been compromised.
Meanwhile, the Tribune said, federal authorities were investigating an unrelated report that hackers had compromised the city's Web site during the weekend. A message posted on Twitter at 6:17 a.m. Sunday under the name "antis3curityops" told people to "fire" on chicagopolice.org and chicagosergeants.org.