The terror group claimed responsibility early Tuesday for the weekend attack outside the Curtis Culwell Center in Garland, Texas.

The group said the two gunmen who died were on a mission, according to reports from the AFP news agency.

ISIS made the statement in an audio release on a radio station.

“Two of the soldiers of the caliphate executed an attack on an art exhibit in Garland, Texas, and this exhibit was portraying negative pictures of the Prophet Mohammed,” AFP quotes the jihadist group as saying.

The group went on to say “We tell America that what is coming will be even bigger and more bitter, and that you will see the soldiers of ISIS do terrible things”, according to AFP.

The gunmen in Garland have been identified as Elton Simpson and Nadir Soofi. The two were roommates from Phoenix.

An off-duty officer working security at the event returned fire – killing both gunmen.

The event the two attacked was called the “First Annual Muhammad Art Exhibit and Contest.”   There were roughly 200 people inside when the shootings happened outside.

Organizers spent up to $10,000 on extra security for the event, according to CBS News.  Officials started planning for potential issues months ago.