Abdul Malik Abdul Kareem

The three men accused of plotting an attack at a Prophet Muhammad cartoon contest in Texas had been making plans for months.

The men were friends outside of a Phoenix mosque lighting off fireworks during a New Year’s Eve celebration when authorities said they expressed a desire to make pipe bombs, the Associated Press reports.

Two of them were killed in a shootout outside of the cartoon contest, and a third, Abdul Malik Abdul Kareem, was arrested last week in Phoenix.

Now investigators are trying to determine whether anyone else was involved.