PULLMAN, Wash. -

Pullman police confirm they are not ruling out a friend of Dr. David Warner's as a possible suspect in his beating last month that sent him to the hospital in critical condition.

They are looking at the involvement of Warner's friend, Lawrence McDonald, who was with him the night of the assault. Authorities say the investigation is ongoing and that nothing is off the table.

Court documents reveal the incident started as a shouting match between Lawrence, a Tae Kwon Do club instructor at WSU, and three of the suspects.

Warner, a WSU instructor, tried to diffuse the situation but was punched and tackled instead.

While investigators are looking into his involvement in the incident, Lawrence hasn't been arrested and no criminal charges have been filed against him.

Police said they have other surveillance video from the night of the assault, which may shed some additional light on what happened, but they haven't released that video to the public.

An update in the case is expected sometime next week.