The man suspected of setting fires in ballot drop boxes in Oregon and Washington state is an experienced metalworker and may be planning additional attacks, authorities said Wednesday.

Investigators believe the man who set the incendiary devices at ballot boxes in Portland, Oregon, and nearby Vancouver, Washington, had a “wealth of experience” in metal fabrication and welding, said Portland Police Bureau spokesperson Mike Benner.

The way the devices were constructed and the way they were attached to the metal drop boxes showed that expertise, Benner said.

Authorities described the suspect as a white man, age 30 to 40, who is balding or has very short hair.