(CNN) The mayor of a Seattle suburb was attacked at a party this weekend because of his pro-immigrant stance -- an incident that police are investigating as a hate crime.

Burien Mayor Jimmy Matta was downtown for an annual community event Saturday. An older white man grabbed him by the neck from behind and pushed him to the ground, the city said in a statement

The man told Matta he "wasn't going to let your people take over" and that "illegals aren't going to take over our community," Burien Police Chief Ted Boe told reporters.

Matta said he was attacked because he supports Burien's sanctuary city status and because he is Latino. As a sanctuary city, Burien city staff and police personnel can't ask or collect information about a person's immigration status or religion.

"We have no room for this behavior. It's behavior that we're concerned about," Matta said at a news conference Monday.

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