"It's a fair assumption that that was one of the driving factors, or whether he was trying to make a statement for ISIS or he was just a very sickened, deranged person, I don't know."

Forty-nine people were killed and 53 injured when Omar Mateen walked into the venue and open fired on partygoers.

There's been reluctance from leaders, journalists, and other commentators around the world to call the shooting 'homophobic', which prompted The Guardian journalist Owen Jones to storm out of a live TV panel programme which was discussing the attack.

Mr Key it "may" have been a homophobic attack, but didn't have the information to support that view.

Labour leader Andrew Little emphatically says Mateen's massacre was homophobic, and he's baffled at Mr Key's comments.

"I don't know how you could possibly draw that conclusion; it clearly was. This was a guy who, according to the reports, clearly had difficulty accepting the right of people to express their sexuality, he chose a gay nightclub, he killed gay people," says Mr Little.

Asked if there's a problem with homophobia in New Zealand, both leaders said LGBT communities are "tolerated" by Kiwis.

"I think New Zealand's a lot more tolerant I mean if you think about when I passed the marriage equality Bill in New Zealand you didn't see a particular backlash, I was a centre-right political leader that supported that change and there wasn't a change in support for me or the Government as a result of doing that," Mr Key says.