Further criminal damage to the building was also reported, with a number of windows also being smashed in the attack.
“This is a sickening display of nothing other than posturing and cowardice, from those acting on no principle other than that of destruction and needless violence,” said Mr Mathison.
“No one deserves to feel threatened or intimidated just for going to work and doing their job, and my thoughts and solidarity are with Mr Hamill.
“It’s eerily reminiscent the dark days of our past here in Northern Ireland, and we mustn’t allow ourselves to be dragged back to those times. This needs to be unequivocally condemned by all across society. There’s absolutely no justification for it.
“I’d urge anyone in the area who has any potentially useful information that may help the police in bringing those responsible to justice, to please get in touch with the PSNI or report what they know anonymously via Crimestoppers.”