New York, June 6 -- : Fifty-seven police officers in Buffalo, New York, have resigned from the force's emergency response team following the suspension of two officers who allegedly pushed a 75-year-old protester to the ground, a source close to the situation informed CNN on Friday (local time).

An investigation is underway in a protest incident Governor Andrew Cuomo called "wholly unjustified and utterly disgraceful." The man was seriously injured.

Video of the demonstration on Thursday showed a row of officers walking toward the man and two pushing him. His head bleeds onto the sidewalk as officers walk past him, some looking down at him.

The demonstrators in Niagara Square were, like those across the country, calling for racial justic...