(CNN) — Arizona investigators surveilling the man accused of shooting at the Democratic National Committee office in a suburb of Phoenix saw him posting political signs with bags of a white, powdery substance attached,

The man arrested in connection to a shooting at the Democratic National Committee’s (DNC) field office in Tempe, Ariz., may have been planning a mass casualty event, Maricopa County prosecutor

The suspect was also arrested for allegedly hanging suspicious bags of white power from political signs lined with razor blades.