Police say the driver of a van that exploded outside the headquarters of the Australian Christian Lobby on Wednesday evening was not "politically, religiously or ideologically motivated".
"The driver appears to have ignited gas cylinders within the vehicle, causing an explosion which damaged the vehicle and building," the statement from ACT Policing said.
Police were notified of the explosion around 9.35pm on Wednesday night. No one was in the building at the time, but the incident caused significant damage to the front of the building.
The 35-year-old driver was the only person injured in the blaze, suffering serious burns. After the explosion, he walked from the building in Deakin to Canberra hospital in Garran – a walk that would usually take just under an hour.
He has undergone a short interview with police and is in a critical condition.
ACL managing director Lyle Shelton described the van as a "car bomb" on Twitter and said he was "shocked this could happen in Australia".
"What we know is that someone drove a van loaded with gas cylinders at our office last night and detonated it," Shelton told ABC Radio.
"The ground floor windows of our building were blown out."
In a press conference, ACT Policing deputy chief police officer Mark Walters said "We do not believe there is any threat to the community as a result of this particular incident". He added that the bomb squad had been called to ensure no risk to first responders.
Police are confident there was no political, ideological or religious motive for the explosion, but Walters would not be drawn on reasons for the attack.
A closer view of the car bomb driven into the ACL office in Canberra tonight. Shocked that this could happen in Aus… https://t.co/yViGE0vNq1
The incident comes at the end of a high profile year for Shelton and the Australian Christian Lobby, who have been at the forefront of lobbying against same-sex marriage and the LGBTI anti-bullying program, the Safe Schools Coalition.
"While I don't know the motive of last night's attack, this, coupled with death threats and multiple threats of violence my staff have endured over this year, is extremely unsettling," Shelton told ABC Radio.
He added most of the threats had pertained to his advocacy on LGBTI issues in Australia.
"ACT Policing investigators have been in contact with the ACL staff today and our investigations will continue in relation to any threats that have been made towards the ACL," Walters said.
Prominent supporters of same-sex marriage, who are often up against Shelton in the debate, offered their thoughts to the Australian Christian Lobby on Thursday morning.
Thoughts and prayers are with everyone at the Australian Christian Lobby, shocking and saddening incident.
My thoughts & sympathies are with @LyleShelton & @ACLobby after a horrifying act of violence. Glad all are safe https://t.co/980IHU3IDM
I condemn apparent attack against @ACLobby. It put lives at risk & if politically motivated strikes at the heart of our democracy.