To convey that things are happening at the same time in Japanese, と同時（どうじ）に will often be used. This is a combination of the 格助詞（かくじょし） (case marking particle) と in its 並立（へいりつ） ‘lining up’ use, 同時（どうじ）, a noun meaning ‘the same time’, and に, the 格助詞（かくじょし） marking a location.
と同時（どうじ）に translates as ‘at the same time as (A)’, ‘the instant that (A)’, or ‘as well as (A)’. In sentences that use this grammar structure, (A) is considered to be the primary event, but any (B) or (C) events are not considered any less important.

• サイレンが鳴（な）ったと同時（どうじ）に、犯人（はんにん）は逃（に）げた。
  As the siren went off, the criminal ran away.
• この機械（きかい）は便利（べんり）であると同時に危険（きけん）である為（ため）、気（き）をつけて使用（しよう）してください。
  This machine is useful, but at the same time, it is very dangerous, so please use it with caution.
• その人（ひと）は博士（はかせ）であると同時に宇宙飛行士（うちゅうひこうし）でもある。
  That person is a scientist and also an astronaut.

In the case of nouns and な-Adjectives, である is often omitted.

• 私（わたし）の家（いえ）は自宅（じたく）と同時にオフィスでもある。
  My place is a house, and at the same time it is also my office.

While the literal meaning of と同時（どうじ）に is ‘at the same time’, this expression is also regularly used when listing multiple roles or functions that someone/thing has. This comes across as ‘as well as’, but still carries the ‘at the same time nuance’.

• 野菜（やさい）と同時に肉（にく）を鍋（なべ）に入（い）れてください。
  Please throw the vegetables and meat into the pot.
• カギと同時に携帯（けいたい）をどこかに忘（わす）れてきた。
  I lost my keys as well as my phone somewhere.