Omar Mateen had twice been investigated by the FBI (in 2013 and 2014) for making inflammatory remarks to co-workers about terrorism, and for his alleged ties to Moner Mohammad Abusalha, the first American to carry out a suicide attack in Syria. Both investigations petered out for lack of evidence.

That a nightclub with a predominantly lesbian and gay clientele was deliberately targeted by Mateen will increase demands by America's LGBTI community for greater protections, legal and otherwise.

Similar claims of vulnerability will be heard from other minority groups. Most regrettable of all, Donald Trump's decision to preempt official investigations into the incident and claim credit "for being right on radical Islamic terrorism" threatens to turn a now charged topic into a partisan free-for-all.

There seems little doubt as to the gunman's motive. Minutes before launching his attack, he's reported to have called Orlando police to pledge allegiance to Islamic State. Shouts of "Allahu akbar" were heard during the shooting, and shortly afterwards, IS claimed responsibility in a statement released over an encrypted phone app.

Prior contact does not necessarily indicate direct and extensive links with IS. That would have heightened the risk of detection by authorities. It's more likely Mateen "self-radicalised" and that he acted partly as a result of a pre-Ramadan speech given last month by IS spokesman Abu Muhammad al-Adnani inciting IS supporters to carry out killings abroad during the holy month.

IS-inspired terrorists have been threatening, bashing, terrorising or otherwise killing Jews, homosexuals and liberal Muslims in France and Britain for years. It's one aspect of the hideous IS campaign that does not get the attention of the media or the chattering classes that it warrants.

With an estimated 300 million guns in the US, the challenge the FBI faces in preventing further attacks like San Bernadino and Orlando is enormous.

Orlando will precipitate further debate about tightening America's gun laws, led by President Barack Obama. History, however, suggests meaningful reforms will not eventuate.

More critical at this juncture, however, is the necessity to treat this matter as a crime and not as a pretext for recrimination.