In the email exchange, which was originally revealed by the website ThinkProgress, Steve Bracknell, who heads the police department in Lake Mary where Zimmerman lives, endorsed his correspondent's statements that Zimmerman is a "ticking time bomb" and "a Sandy Hook, Aurora waiting to happen."
Since he was acquitted this summer of killing Trayvon Martin, an unarmed black 17-year-old, Zimmerman has been in the news several times. These include two stops for speeding, a visit to the Florida factory where the gun he used to kill Martin was made and, most recently, an alleged domestic violence incident involving his estranged wife.
Interviewed Thursday by NBC News, Bracknell said the exchange was genuine, MSNBC reported. But he said he was trying to reassure Santiago Rodriguez, who he described as a "concerned citizen."
Bracknell told Santiago he would revoke Zimmerman's concealed carry permit if he had the legal authority.
"I have some concerns," the police chief told NBC News. "I think a lot of people do."
Police are still deciding whether to bring charges against Zimmerman for the incident Monday. Shelley Zimmerman told a 911 dispatcher that her husband had threatened her and her father with a gun, although she later said she had not seen a weapon and police did not find one on his person.
Bracknell told NBC officers were not legally able to search Zimmerman's car. He said Zimmerman had a gun when he was stopped for speeding.
"Does anyone else except me see a pattern? The word firearm keeps popping up," he said.