The Daily Fail is going all-out on the Islam speculation.
‘We consider this an act of terrorism’: Suspected Islamic extremist shoots dead at least 20 dead at Florida gay club after bursting in ‘wearing a suicide vest’ and taking hostages - injuring a further 42

They use an exact quote to support this, but their attribution is a bit less than precise:

the FBI believe he may have ‘leanings to radical Islamic terrorism’.