In order to say that something "just now" occurred, use the time noun 刚才 (gāngcái). It can be placed in front of the verb or the subject of a statement.
This grammar structure is pretty straightforward. Similar to the English "just now," you can put 刚才 (gāngcái) right before the verb in a sentence. It can also come before or after the subject.
Structure: 刚才 + Verb
Examples:
你刚才说什么了?(nǐ gāngcái shuō shénme le) = What did you just say?
刚才谁来了?(gāngcái shéi lái le) = Who came just now?
刚才你去哪儿了?(gāngcái nǐ qù nǎr le) = Where did you go just now?
刚才我去洗手间了。(gāngcái wǒ qù xǐshǒujiān le) = I just went to the restroom.
老板刚才生气了。(lǎobǎn gāngcái shēngqì le) = The boss just got angry.
你们刚才在看 什么?(nǐmen gāngcái zài kàn shénme) = What were you looking at just now?
不好意思,我刚才出去了。(bù hǎoyìsi, wǒ gāngcái chūqù le) = I'm sorry, I just now stepped out.
宝宝刚才哭了。(bǎobao gāngcái kū le) = The baby just cried.
他们刚才去开会了。(tāmen gāngcái qù kāihuì le) = They just went to a meeting.
刚才有人找你。(gāngcái yǒu rén zhǎo nǐ) = Just now, there was someone looking for you.
Note that for all of those cases, we're talking about something that happened just now, within the past 5 minutes or so. If you're talking about something that "just happened" yesterday or last week, don't use 刚才 (gāngcái), use 刚 (gāng).
Credit: mandarinmorning