They have the name of one of the suspects Farooq saeed, but apparently authorities have refused to speculate on weather its ISIS related.
A quote from ISIS a while back
“We have 71 trained soldiers in 15 different states ready at our word to attack any target we desire. Out of the 71 trained soldiers 23 have signed up for missions like Sunday, We are increasing in number bithnillah [if God wills]. Of the 15 states, 5 we will name… Virginia, Maryland, Illinois, California, and Michigan…The next six months will be interesting.”