I was at the protests in Seoul against martial law. Here's what I saw.

• Andrew Minjun Park, 27, is a graduate student at Seoul National University.
• Park joined the protests in Seoul after South Korea's president abruptly declared martial law.
• He arrived at the National Assembly at about 11:45 p.m. Tuesday and stayed until the next morning.

This as-told-to essay is based on a conversation with Andrew Minjun Park, 27, a graduate student at Seoul National University. Park participated in the protests against martial law outside South Korea's National Assembly building on Tuesday night. The following has been edited for length and clarity.

I was preparing for my political science Ph.D. applications on Tuesday when I heard the news about South Korean President Yoon Suk Yeol declaring martial law.

At first, I thought it was fake news. Putting the country under martial law is something that's often associated with the authoritarian governments South Korea had in the '70s and '80s.

But after watching the president's address on YouTube, I realized he was dead serious.

To me, this was a critical moment in Korea's modern history

Initially, I didn't want to join the protests that were forming outside the National Assembly building.

There was a possibility the protests could turn violent. You could also get arrested since protests are illegal under martial law.

But as more and more photos of security forces descending on the building came in, it began to dawn on me that this situation couldn't be taken lightly.

The president had crossed the line when he got the military involved. What he had done posed a risk to democracy.

To me, this was a critical moment in Korea's modern history.

I knew I would regret it for the rest of my life if I didn't head down to the National Assembly.

The protests were scattered at first

I took the subway to the National Assembly. Unlike most nights, the train was packed. I think a few hundred people got off with me at the station when we arrived.

By the time I got to the building, it was around 11:45 p.m.

There was a police bus parked in front of the building's gate to prevent protesters from entering the National Assembly. I also saw helicopters flying over the building.

At first, the protests were scattered. Some groups were near the gate, while others were lingering behind. There didn't seem to be any central leadership.

I noticed that many of the people who were already there seemed to be party members or unionists. The unionists were wearing uniforms and waving their unions' flags.

But at around 12:30 a.m. or so, I started to see families and students arriving in larger numbers. Some parents brought their children along.

This was my first protest, and I wasn't prepared for the physical aspects of it.

It was really cold, and my hands hurt from trying to hold up a banner I had made. And because it was so crowded, I kept bumping into people.

When the National Assembly voted unanimously to block the president's decree, the protests' agenda began to shift toward calling for the arrest and impeachment of President Yoon.

The protests took place in a peaceful manner.

At around 4:30 a.m. or so, the president announced he would lift martial law and withdraw the troops. Cheers broke out among the protesters. That was when I decided to take a cab back home.

The situation is not over yet

After getting home, I called my parents to tell them I had gone to the protests. I had originally told them that I wasn't going to participate in the protests because I could tell they were worried.

They told me I had made the right decision in going. Both of my parents lived through martial law when they were young.

I am wary of what could happen next. There have been calls for President Yoon to resign and for him to be impeached or indicted.

If there are more protests calling for Yoon's removal, I think I will definitely be there, too.