my grandma has bipolar disorder and has been taking medicine for it for years. 

she has a habit of constantly and repetitively cleaning, mopping the floor, doing the dishes, etc. so, when she saw that my grandpa's desk was full of papers, she wanted to tidy them. he told her not to but she insisted that she did. it escalated very quickly when she was trying to remove the papers and he told her not to, an argument ensued.

my uncle came in between them to calm them down and stop their fighting, but my grandma went into the kitchen and grabbed a knife, and threatened my uncle with it, all while behaving very angrily. she followed him onto the street with it and the police had to be called, she was then admitted into a hospital for a couple of weeks.

ever since this incident i've been very afraid around her and i was wondering if this was what a manic episode was. did it happen because she wasn't taking meds? or is it normal to have an episode even while on meds?