Cook said officers stopped several offenders attempting to leave the store and four were arrested.
While taking the group into custody, one of the offenders attempted to push his way past, he said.
“He has acted aggressively towards one of the staff and assaulted a member of the public who had tried to assist.
“Another offender spat at another constable at the scene.”
Two 16-year-old girls and two boys, aged 13 and 16, were arrested.
Cook said the aggressive behaviour was “unacceptable” and the youths would be held to account through the Youth Aid process.
He said police were unable to identify the member of the public who had tried to help, as he left the scene shortly afterwards.
Police are also looking for a fifth offender, who fled from the store.
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