A teenage parkourist from New Jersey surpassed the World Trade Center's $40 million security system and was able to climb to the top. How did he do it?

Justin Casquejo, a 16-year-old New Jersey parkourist, was arrested for sneaking past security at 1 World Trade Center and spent two hours on Sunday morning climbing to the top of the 1,776-foot tower, which is still under construction, the New York Times reports.

One World Trade Center has a security system estimated to cost at least $40 million, including "a state-of-the-art integrated security system that includes closed-circuit television, coupled with video analytics to detect abnormal situations; digital recorders; access control systems; provisions for chemical, biological and radiation detection; a fiber-optic backbone and network; and related electrical infrastructure," The Village Voice reports.

But the security system meant nothing to Casquejo, who slipped past a sleeping guard on duty around 4:10 a.m. According to Port Authority Police Spokesperson Joe Pentangelo, Casquejo "climbed through a one foot square opening, which is in the exterior construction fence surrounding the World Trade Center. He is able to enter undetected by climbing scaffolding.

"Somehow he is able to gain access to the interior of the building, and he encounters a security guard on the 104th floor." The security guard, Pentangelo says, "has been characterized as inattentive during this incident."

He was fired.

Casquejo was in 1 World Trade Center for almost two hours before he was arrested by Port Authority Police at 6 a.m, The Village Voice reports. 

Casquejo got a lift up the tower from a union elevator operator, even though he had no ID, the New York Post reports. The elevator took him to the 88th floor and from there he took the stairs up to the 104th floor, where the guard on duty was sleeping.

According to the criminal complaint, Casquejo told the arresting officer he climbed all the way to the antenna before they caught up with him.

The officers seized both Casquejo's camera and a cell phone.

The security at 1 World Trade Center -- which was previously believed to be impenetrable -- is now under investigation, ABC News reports.