Witnesses of an alleged assault in Auckland's Papatoetoe say they're in shock after seeing the violence

One person is in a critical condition and another in a moderate condition after the incident at Z Energy on Hunter's Corner just after 1pm.

Police say a suspect attacked the pair with a weapon.

A woman who saw the frightening act says it involved two groups, a man and a woman in one, and four people in the other.

She says the weapon used was sharp - but couldn't describe it any further.