He said: “You know, you wish for a nice school shooting to interrupt the monopoly.”
Mr Bonniwell was quickly admonished by his co-host, Julie Hayden, who said: “No, don’t even say that! Don’t call us! Chuck didn’t say that.”
In an attempt to backtrack, Mr Bonniwell said he was referring to shootings “in which no one would be hurt”, reported local news site Colorado Times Recorder.
A reporter for the site called the program anyway and was told by Ms Hayden that her co-host “immediately wished he hadn’t said [it]”.
Radio station 710 KNUS Denver said in a statement: “Given the history of school violence that has plagued our community, 710 KNUS confirms that an inappropriate comment was made on the Chuck & Julie show by co-host Chuck Bonniwell.
“A programming decision was made to end the program immediately.”
According to The Denver Post, the co-host made a statement on the program’s Twitter account, which was later deleted: “I made an inappropriate comment meant as a joke. I’m sorry it was not received that way.”
Calls for the radio station to fire Mr Bonniwell have proliferated on social media, with some calling his comments “heartless” and “stupid”.
— John Ronquillo (@johnron4co)
“Chuck Bonniwell, ‘joking’ about a school shooting makes you sound like a monster. I hope you lose your job over this, you should not have a microphone,” said a person on Twitter.
Another commented: “If Chuck Bonniwell was a Muslim he’d be arrested for making terrorist threats. But, he’s a white conservative so we’ll sit and wait to see if he radicalised someone.”
There have been 409 mass shootings in the US this year resulting in 486 deaths. 18 of those shootings took place in schools or universities.
The last school shooting to occur in Colorado was in May this year, in Highlands Ranch where nine people were shot and one died.