[2] Willem van Spronsen (1950–2019) was a carpenter and a resident of Vashon, Washington,[6][1] who had been arrested previously during a demonstration at the same ICE detention center in June 2018.

[1] According to police, van Spronsen was an anarchist who claimed to be associated with a designation known as antifa, a broad category of antifascist action frequently mistaken for an organized group.

"[9] Van Spronsen's daughter, who describes herself as an advocate of liberal pacifism, said her father was a supporter of anarchism but had written that she disagreed with him "on some principles, such as the use of force and weapons in the fight".

[13] The GEO Group, which runs the facility, called the attack an act of terrorism in a public statement they released saying "This video footage shows the seriousness of the threat to our employees and immigrants housed at the Tacoma Processing Center.

"[14] Seth Jones, a terrorism analyst at the Center for Strategic and International Studies, said of the attack and of Van Spronsen's beliefs "The problem is not that people have views that are against fascism, against white supremacy, against racism.