"Each reaction ... he sits in his cell in the smug comfort of knowing he has impacted on everyday Kiwi life."
Casson goes on to advise New Zealanders against mourning the loss of those killed in the attack - saying that in doing so, they're letting the alleged gunman "win".
"Let's move on as a nation, never forget or forgive but strive to live as normal," the post concluded.
The deleted post wasn't Cassons' first public criticism of the way officials and the public reacted in the aftermath of the shootings.
A post on the Facebook page published the day after the incident discussed a vigil at Hamilton's Claudelands Park - which Casson made clear he would not attend.
"I am sure it will be safe but I do not want this to turn into a political showcase either, it is not the time for that sort of stuff," he wrote.
"The most effective way of showing such acts of terrorism that we are strong and united is to carry on with daily life normally."
Responding to Casson's latest post, which had been screen-shot and posted on Twitter, Hamilton City Council said he was entitled to share his view on his own channels.
"The council stands with NZ on this," it said.
Casson did not respond to a call from the Herald.
But in a subsequent post on Facebook, he wrote: "I never said we should not come together or only commemorate once, but our way of life has changed which is very sad, that's what terrorists want."
He added that "we as New Zealanders and that includes all cultures that call NZ home have to move on as a nation" and "flip the bird" at the person responsible "and not be afraid".
Casson is a first-time councillor - a role he took on after a 26-year service with the police force.
This included four years as the officer in charge of the Hamilton North Community Policing Centre.
During his time in the police force he took on international peacekeeping roles in countries including Papua New Guinea, Tonga and the Soloman Islands. He is also a trained diplomatic protection officer.
He has six children with his wife, Debbie, and is a keen sportsman.
A blurb for the councillor on the Hamilton City Council website said he was "not a shrinking violet".
"If I identify something that is wrong I will speak up," it said.