If a guy you knew for awile usually doesnt open up to you then one day?

Guy usually is very reserved and won't tell me anything to much about his personal life. However on Friday he came over and he opened up to me talking about how he doesn't trust anyone, his goals in life, his child hood, his sister just having a baby, problems he has had in the past with friends, etc. What does this mean when someone begins sharing this type of stuff with you? Does it mean he will develope an attachment to me if he keeps doing this and why did he decide to do this? Emotionally for him what does it mean?