With thanks to Jade the Terrible:

If you see ICE agents firsthand in Washington state:

1) Alert folks in the area, then
2) Call the WA Immigrant Solidarity Network hotline at 844.724.3737 or text "ICE" or "Migra" to 509.300.4959.

The hotline is staffed 7 days a week from 6AM - 9 PM.