But Sunday night, just off-campus, as he was walking home from the library, Zachary's life came to a sudden and violent end. He was shot and killed in a robbery. His laptop and cell phone were stolen. Police believe two men were involved -- a driver and a gunman.
Now Zachary's father, Dan Marco, has a plea: "I want the kid that killed my son, and I realize there's a tandem there, but I also realize one pulled the trigger and I want that guy."
And to catch the guy who "pulled the trigger," Dan Marco went on TV to make a stunning gesture. He promised to help find a lawyer for one of the men responsible for his son's death -- the driver of the getaway car -- in return for the identity of his son's killer.
Dan Marco said, "What I offer to him is that, if he comes forward, I will do my best to ensure that he gets the best defense possible and gets a deal that allows him to see the light of day again."
Marco is a criminal defense attorney. Few doubt his determination or his ability to find the accomplice a good attorney, notes "Early Show" co-anchor Erica Hill. It's an unusual offer, but for Dan Marco, it may be the price of justice for his son.
Zachary was killed on a well-lighted street. Police still don't know how the robbery escalated to murder.
But how did Dan Marco come up with his idea?
On "The Early Show" he said he thought of it "because I don't sleep. I have plenty of time to think."
He added, "I know that the Tempe (Ariz.) Police Department is doing their best. They have 12 detectives working on numerous leads. The inevitability of their capture is certain. However, I would like to speed it up."
As for the people involved in his son's death, Dan Marco said, "These are people who live in a world of no honor. And one of them is -- the inevitability of one of them rolling is certain. And so, what I'm trying to do is to tell the guy, 'Look, there's a felony murder law in Arizona. If you participate in a felony that ends up in the death of -- in someone's death, whether or not you pulled the trigger, you are as guilty of murder as the guy that pulled the trigger.' And what I'm saying to him is, 'The noose is tightening, let's end this, come on in, tell us who did it. And you're going to have somebody advocating on your side.'
"The Arizona constitution has a victim's bill of rights that gives the victim and unfortunately, I can only speak for my son, a lot of power or a lot of input in the process. We participate in plea negotiations. We get to speak at every hearing. I will do everything that I can that assures that you see the light of day again -- just come in and tell."
How does Dan Marco deal with the thought the he may have to help someone involved in a crime that led to his son's death?
"Emotionally and intellectually, it's difficult," he said. "But, I'll do anything for my son, for justice in this case."
Katie and Michelle Marco, Zachary's sisters, also appeared on "The Early Show."
Michelle said she supports her father's actions.
"I agree with him," she said. "I just want to find out who did this to my brother and I just want some justice."
Katie said, "To say my brother was a hard worker was a complete understatement. Like no matter what time of day I called him, he was always whispering on the phone because he was in the library or in class and -- and he was -- he was a really great brother. Like he pushed us to our full potential because he wanted what was best for us and he wanted us to have a good life."
Dan Marco said he's grieving for his son while continuing to seeking justice.
"I am in a constant grieving process, but look, my son was one of the most driven and focused individuals that I've ever met in my entire life," he said. "And what I'm doing now is less than he would have done for me, I know it. So, that is grief."
If Dan Marco could speak to the person who was involved in the theft, but didn't kill his son, he said it would be this: "The inevitability of your capture is certain. The blessing of coming in and getting this off your conscience -- they don't have a conscience, who am I kidding -- you have a very small window, a very small window and a very small opportunity that's being offered to you. Come in, because this is it. If the police have to catch you, the police have to arrest you, all bets are off and, trust me, as hard as I'd work for you, I will work against you. And right now, you are looking at life in prison and potentially execution, depending on the circumstances of this case. Come in now because this is it, this is your one chance."