I was doing V1 and then V2 happened: (하)다가
A/V + 다가 shows that one action/state was interrupted or ended because a second started. Note that A/V must be in dictionary form, and the subject must be the same in both clauses. It is often used with 갔다, 왔다 and 있다 — the latter translates as ‘and later on’ (lit: and then after existing):
사무실에서 일을 하다가 화재 경보가 울렸어서 대피해야 됐어요.
I was working in the office when a fire alarm went off and I had to evacuate the building.
운전하다가 타이어를 펑크 냈어요.
I got a flat tire while I was driving.
운동을 하다가 종아리에 쥐가 났어요.
I got a cramp in my calf while working out.
텔레비전을 보다가 전화를 받았어요.
I was watching TV when I got a phone call.
날씨가 따뜻하다가 갑자기 비가 왔어요.
The weather was warm, but it suddenly rained.
책을 읽다가 잠이 들었어요.
I fell asleep while reading a book.
가구를 옮기다가 허리가 아파서 침대에 누웠어요.
When I was moving the furniture I hurt my back, so I lay down in bed.
요리하다가 뜨거운 물에 손을 데었어요.
I burned my hand in hot water when I was cooking.
양파를 썰다가 손가락을 베었어요.
I cut my finger when I was chopping onions.
집에 돌아가다가 슈퍼 밖에 친구를 우연히 봐서 이야기를 했어요.
On my way home, I ran into a friend outside the supermarket, so we talked.
집을 청소하다가 신분증을 찾았어요.
I found my ID while cleaning the house.
친구가 한국에 2년 동안 있다가 나갈 것이라고 했어요.
My friend said that in two years he will leave Korea.
친구의 생일 파티에 갔다가 저는 취하도록 술을 마셨어요.
I went to my friend’s birthday party and drank to the point that I was drunk.
학생들은 교실에 늦게 왔다가 일찍 갔어요.
The students came to the classroom late and left early.
저는 초등학교 선생님 이었다가 진로를 바꿨어요.
I was a primary school teacher and then I changed my career.