But Monday night at his father's office, just minutes from their home, a single gunshot would end it all.
"Around 8 o'clock I heard Christopher come in with two of his friends. They went upstairs. There was nothing out of the ordinary," Dr. John Tas, the building owner, said.
Three hours later, police say, Christopher Yang fired one shot from a handgun, hitting himself in the head.
His two friends called 911, but it was too late. Yang was pronounced dead at the hospital.
Bloody foot prints still mark the floor outside of his father's office. A trash bag full of blood soaked towels sits in the hallway bathroom.
"Disbelief. I couldn't immediately put it into context. It's something that's not supposed to happen," family friend Richard Criscione said.
Criscione is the super at the building where Christopher lived with his parents and brother.
He saw Christopher's mother shortly after she got the news.
"She was numb. She was obviously distraught. She had been traumatized," he said.
Police say the gun was not registered in New Jersey and Christopher's father was away on business in China.
But a look at the teen's MySpace account shows he was no stranger to guns.
One picture shows him shooting a high powered rifle. Another photo shows a table full of assault rifles.
Under interests, Christopher wrote, "Let's start off with guns. I love them. They are my life blood, then it's video games."
No telling why he had a gun Monday night, but Richard, who watched Chrisopher, grow up says this had to be an accident because he would never intentionally shoot himself.
"Children - and that's what he is at 18, a child - can make mistakes, and sometimes you don't get a second chance," he said.