What is the translation for "s'eran"? I cannot seem to find any translation. Thank you

What is the translation for “s’eran”? I cannot seem to find any translation. Thank you.

si erano.
Dice che si erano nascosti e mi hanno sentito urlare.
He says they were hiding and then they heard me yelling at them.

“Erano” is the third plural person of Imperfect of verb “essere”. “S’erano” derives from “esserci”.