A suspected car bomb at the Australian Christian Lobby's Canberra office wasn't politically, religiously or ideologically motivated, police believe.
Windows are blown out and furnishings destroyed at the office in Deakin after it was rammed by a van carrying gas bottles about 9.35pm on Wednesday.
The driver, a 35-year-old local, took himself to the Canberra Hospital, suffering serious burn injuries and he remains there in a critical condition.
"As a result of our conversations with the man, we have been able to establish that his actions were not politically, religiously or ideologically motivated," Deputy Chief Police Officer Commander Mark Walters told reporters.
The group's director, Lyle Shelton, says the apparent bomb follows a year of death threats over its opposition to gay marriage and the Safe Schools program that aims to reduce bullying of gay students.
One of those threats was tracked to a person in Tasmania but the rest were unable to be tracked, he said.
Police have now been in contact with ACL staff and investigations will continue into threats it has received.
An emotional Mr Shelton arrived at the Eternity House building on Campion Street on Thursday morning, having broken his holiday in Brisbane, to find the scene worse than he expected.
"This is not the Australia that I grew up in," he told reporters.
Mr Shelton blamed the left side of politics for potentially fuelling the attack, saying its "name-calling" during the gay marriage debate was unhelpful.
"When members of parliament, particularly on the extreme left, refer to us in the parliament as hate groups, as bigots, I'm sure that doesn't help the situation," he said.
"If there are people who are a bit unhinged out there, that sort of rhetoric doesn't help.
"As a society we've got to have civil debate, we've got to stop the name-calling and the slurs."
Mr Shelton said the ACL would remain defiant in the face of what he believed was a deliberate attempt to silence it.
"I'm sure it's a message to intimidate us and cause us to be silent in the public square and that's something we're not prepared to do.
"It's more important than ever that we have our voice involved in the public discourse."
There have been condolences from all sides of politics, including independent NSW MP and marriage equality campaigner Alex Greenwich.
"Thoughts and prayers are with everyone at the Australian Christian Lobby, shocking and saddening incident," he tweeted.
Pauline Hanson described it as a "cowardly attack" while coalition backbencher George Christensen also took to Twitter saying if the attack was politically motivated, "it is disgraceful and should be denounced".