(Portland, OR) -- An investigation is ongoing into a large fight involving Patriot Prayer leader Joey Gibson in which a woman was allegedly knocked unconscious. Police responded to the area of Northeast 8th Avenue and Couch Street around 7:30 last night for the fight involving about 60 people. Cellphone video obtained by KATU shows Gibson and several other people sparring with members of another group wearing handkerchiefs over their mouths. A woman is seen walking up to Gibson's group before apparently being struck off-camera and falling to the ground. Police say they're reviewing footage to determine if charges should be filed. The fight capped off a mostly peaceful day of May Day marches and demonstrations.