Romeo is an impulsive character who lets his emotions dictates his actions.

“This day’s black fate on moe days doth depend, This but begins the woe others must end.”

Romeos being impulsive by talking about to kill everyone “This day’s black fate on moe days doth depend, This but begins the woe others must end.” this will not solve anything by killing people that’s why he’s acting on his emotions instead of thinking.