The other answers are mainly correct, but they leave out the part that this is usage of 黙っとる or 黙っとれ are still common in certain dialects, mainly western Japan. Some say the dividing line is somewhere between Shizuoka prefecture and Aichi prefecture. Once you go west of Aichi prefecture you hear the とる form a lot, like in phrases as 知っとる (知っている) or やっとる (やっている). Basically, in 標準語 the おる form has been replaced by いる but remains in dialects still.

The other answers are mainly correct, but they leave out the part that this is usage of 黙っとる or 黙っとれ are still common in certain dialects, mainly western Japan. Some say the dividing line is somewhere between Shizuoka prefecture and Aichi prefecture. Once you go west of Aichi prefecture you hear the とる form a lot, like in phrases as 知っとる (知っている) or やっとる (やっている). Basically, in 標準語 the おる form has been replaced by いる but remains in dialects still.

However, Japanese has a lot of different ways of saying that expression. For example:

黙ってろ

黙っとき

黙っとけ

黙っとりゃあ

黙りなさい

Some of these are dialectical and have slightly different use cases.