He was the second man. He was killed in this away.

→ He was the second man who was killed in this way.

There were some noisy people in the audience and one of them kept interrupting the speaker.

→ There were some noisy people who were in the audience kept interrupting the speaker. 

My friends, Lam and Bich got married on a bright sunny Sunday.

→ The day on which Lam and Bich got married was a bright sunny Sunday.

You left the key in the office. That was very careless of you.

→ You left the key in the office which was very careless of you.

They are living in a city with a population of 14 million.

→ They are living in a city where had a population of 14 millions.

He was the second man who was killed in this way.

One of the noisy people who were in the audience kept interrupting the speaker

The day on which (my friends,) Lam and Bich got married was a bright sunny Sunday.

you left the key in the office which was very careless of you