The chaotic world suddenly became incredibly quiet when an unknown "bomb" thrown from anti-extradition bill protesters hit my neck from behind. I couldn't move and the dizziness lasted about 10 seconds.

Gradually regaining consciousness, I still managed to capture the moments when clashes raged on between radical protesters and police officers in Wong Tai Sin – a working-class residential district of Hong Kong — on Saturday midnight.

Working as a press photographer in Hong Kong has become more challenging. The escalating violence in recent protests made me aware of a fact: you never know what kind of danger you might run into in the next minute.

The important and painful lesson I learned from my experience on Saturday is that I have paid serious attention to the protesters' self-made weapons. They are upgrading them.

Those lethal weapons used by radical protesters in the unrest in Tsim Sha Tsui - one of the city's busiest tourism attractions - really stunned me.

Outside the besieged Tsim Sha Tsui Police Station, I saw three masked and fully-geared protesters controlling a giant slingshot, which has never been seen in previous marches. They were trying to shoot bricks and stones into the police station premises.

At one moment I felt I time traveled to an ancient war. The soldiers are trying to conquer a town with a trebuchet.

The dangerous weapon scared all journalists who surrounded the three as the slingshot is tremendously powerful and the operators often shot items into the wrong directions. The three "not well trained" crazy protesters might hurt passers-by, journalists or anyone in each shot.

Moreover, compared with previous protests, many more protesters were equipped with deadly weapons including metal rods and slingshots. Some of them surrounded the police stations and constantly escalate their defiant acts. Some of them in Mong Kok even attempted to lit a fire on streets with machine oil.

Their knowledge may not be enough for them to understand arson is a crime punishable by life imprisonment.

In addition to the weapons, I found well prepared and well-organized groups of protesters tried to expand the impact of their rallies with "flash mob" tactics.

From noon to late night on Saturday, following the protesters, I have to go back and forth in Mong Kok, Tsim Sha Tsui, two densely populated business districts in Hong Kong, and Hung Hom.

Some protesters flooded into Hung Hom and blocked the entrance of Cross-Harbour Tunnel - one of three critical traffic arteries between Hong Kong Island and Kowloon – twice on Saturday, from about 6:00 pm to 7:00 pm and from 10:00 pm to 10:30 pm.

The "flash mob" tactics caused traffic congestion in broader areas and also made it difficult for the police to deal with.

The escalated violence made me worry about potential bloody incidents waiting to happen, hopefully not on Monday, when protesters called for a city-wide strike and mass rallies in different districts.

As Hong Kong residents, each of us has his or her responsibility to safeguard the city's public order and do not put others' life at risk. I hope people can be responsible for themselves and for the city, so that it can resume peace and rationality.