Colin was always a mild-mannered man. suddenly his behavior changed radically. he instigated fights and was verbally abusive to the people around him. it is likely that john's problem initiated in his

Amygdala

Explanation:

Amygdala is the part of the brain. It plays a vital role in brain functioning. Amygdala is specifically known for emotions. Amygdala is the part of the limbic system in the brain. This part of the brain has two different roles. It functions both in pleasure and fear emotions. It works the same in both animals and human beings.

It is related o the aggressive behavior in animals. When castration has done in males it shrinks around 30%. When stress, anxiety, depression, post-traumatic stress disorder, and other disorder occur, it has been considering that it happened because of the dysfunction in the amygdala.  

So that Collin was not a mannered man. but suddenly his behavior has been changed. He starts to abuse people. This problem does because dysfunction occurs in the amygdala.

so you know what happened be fore you were alive

explanation:

if you are on the computer you can not take a picture but you can upload one but i am not sure about phones but i'm pretty sure it's the but to upload one just click the paper clip looking thing/ link thingy thing and upload a pic