How did this happen?

I'm still not sure why Son2 decided to try heroin or exactly when.  I've found out a lot of painful things when he admitted them to us, and this is my best guess as to what happened.

The summer before his senior year in high school I think Son2 was in a bit of a slump, down in the dumps. A girl he really cared about had dumped him, and it hit him pretty hard, he started hanging out with different people and getting into a little trouble here and there.  He was never a straight-A student, but his grades did slide a bit.  We caught him lying about where he was.  When school started, he dyed his hair.  We thought he was just spreading his wings, trying to be his own man or something.  I believe some time that summer or during that school year, he started experimenting with drugs.  My guess is he had already been drinking.  We did catch him with beer sometime during that school year.  The drugs started with prescription drugs from our house.  He had his wisdom teeth pulled that summer, and got a real kick out of the sedative.  He didn't need the painkillers at the time, so I never even noticed that they were gone at some point.  Later in the school year I broke my foot, and was prescribed a narcotic painkiller.  I used some, but there quite a few left.  It was months and months before I realized they were missing from the bed stand, didn't really think about it until after he confessed his heroin addiction.  Apparently he found some "friends" at school that were doing the same and they traded pills.  I believe they swallowed or crushed and snorted them.

At some point, he decided to try heroin, I'm not sure when, but it was before he went off to college.  Not sure how much, but he was using the summer before college.  It is amazing, but somehow he managed to beat the drug test and get hired at a convenience store.  He also went on vacation with us to a relatives wedding out of state.  Yes, it's true, all of this happened and we did not know he was on drugs.  I think it got worse, once he left home and went off to college.  He went down hill pretty quickly, was shooting heroin by then, several times a day.  I think he had a couple of near overdoses.  I'd like to think I would have noticed something if he would have been living at home.  I think he tried other drugs, but his drug of choice was heroin.  I think he also sold X or something to try to make some money.  He was going through cash furiously, and he had to know we were gonna notice eventually.  We found all this out later.  As I said, we didn't have a clue at the time.

It's so hard for me to look back at that time period now.  I see myself then in blissful ignorance and remember all the things a kids does his senior year with some resentment.  I think back on many things that happened, things a parent should cherish, like school activities, banquets, sporting events, band concerts, graduation, and think oh, he was probably high, or I wonder where he really went when we thought he was at a school function, or god knows what.