Unfortunately for Obama and his desire to bring in thousands of Syrian Muslims, the simple fact that this latest mass shooting was perpetrated by Muslims - for whatever reason - will drive, right or wrong, the argument and 'justification' NOT to bring the 'refugees' here now.
The fact that these shooters were Muslim yet NOT 'widows and orphans' will drive a narrative / argument against Obama's plan. In response, right or wrong, I predict Obama will move to defuse this narrative by claiming this attack to be a case of 'workplace violence' / 'disgruntled employee' violence, perhaps correctly (we don't know yet).
The fact that they are Muslim, though, will fuel the concern over national security, American safety, Islamic Extremist / ISIS fear, valid or not.
I would like to know from the FBI is this / these individuals were at all among the reported 1,000 open cases of theirs regarding ISIS or if this was just a random / completely unexpected / unsuspected event. My guess right now is these guys were never on the FBI's RADAR.