As we walked on to the campus of Hong Kong Polytechnic University, photojournalist Dan Criswell and I didn't know what to expect. I had seen the pictures but wasn't prepared for what I would see up close. The campus is nothing short of shocking – an eerily quiet abandoned battlefield.

There are makeshift shields attached to railings overlooking the streets below. Battle stations with stocks of petrol bombs, rocks, slingshots and homemade catapults surround the campus.

Rioters set up DIY first aid clinics. There are sleeping quarters in the gymnasium. Destruction is everywhere: smashed glass and political slogans spray painted on walls. Clothes, helmets and protective gear are strewn about. A lone chainsaw sits near an entrance to campus.

There are apparently a couple dozen holdouts staying somewhere on the sprawling campus. We made a cursory search of several buildings but couldn't find anyone. It feels like a zombie movie. Dan and I were on edge as we walked through the abandoned buildings.

Two pastors have been given access to campus and are advising the holdouts, but only see them occasionally.

"Last night we were able to meet a couple and talk to them a little bit…they are OK, mentally and physically," said one pastor.

They say the remaining few fear what will happen if they surrender.

"They are more concerned about their own future, what they are going to face if they come out," said a pastor.

When it becomes clear we won't see the holdouts we leave to file our stories. I don't know if I will return to campus, but I will never forget what I saw at PolyU.