one of my colleague has quit from a company.when I come to this company in 2006,he was my teacher.He teached me a lot.we are the best friend personly.someone said that the colleague can't be the bosom fiend,but I don't think so.
Certainly, And also now that your colleague has quit the company, your can get develop your friendship with him. One of my closes friends used to be my colleague.
you are so lucky that you can take your colleague as a bosom friend.but for me,i have never came across it til now!different perople has their different experience.that's normal.