Giancarlo Esposito as Gustavo Fring in the box cutter scene of AMC's "Breaking Bad"

WARNING: SPOILIERS!

“Breaking Bad” returned for its fourth season last night and wasted no time answering the questions left lingering in the previous season’s finale.

Last year, illegal drug chemist Jesse (Aaron Paul) did in fact murder rival chemist Gale (David Costabile) to prevent their boss Gus (Giancarlo Esposito) from killing both Jesse and his partner Walter White (Bryan Cranston).

But making headlines today is Gus’ reaction to the murder of his other chemist – a 10 minute scene that will surely be one of the most memorable ever of this critically-acclaimed AMC series . [Scroll down to watch in its entirety.]

In the premiere’s most tense sequence, Gus stalked wordlessly around his state-of-the-art meth lab as Walt begged for his and Jesse’s lives. Gus suddenly and brutally used a box cutter to slit the throat of his assistant Victor (Jeremiah Bitsui), who had been seen by witnesses while recovering Jesse from the crime scene at Gale’s house.

The gruesome scene — Gus makes Walt and Jesse watch as Victor bleeds out — almost causes Walt to vomit, but it shows just how confident the creative team behind “Breaking Bad” has become, Esposito says.

“It’s groundbreaking television,” Esposito tells TVGuide.com. “The episode is a mind-blower. I read the script after I received it, and I was shaking; I had to put it down. … It’s brutal and quiet and subtle. So, it’s very, very unsettling.”

As for why Gus would kill one of his right-hand men, instead of the relatively new-to-the-operation Walt and Jesse, Esposito says it’s a no-brainer. “This had to be done,” he says. “Someone did something — they got seen. … So it was about preserving a family; it was about survival. This had to be done, but I could do it in a way that also sent a message to the people who weren’t listening.

“It’s a proving moment for Gus, because we’ve never seen Gus do something so formidable,” Esposito continues.  “This is the final chance that Gus is giving Walt to step up. He’s giving him a warning. He’s saying, ‘Listen: Do it my way, and you’ll be all right.’ It is a moment where Walt could step up and really embrace a part of him that’s Heisenberg.”

Instead, Walt’s reaction will be to go on the offensive. In next week’s episode, he buys a gun for protection, but it’s pretty clear that there’s also a bullet with Gus’ name on it. “Walt knows that his time is limited,” Cranston says. “He knows that, given the opportunity, Gus will kill him and get rid of him.”

Adds Esposito: “There will be a huge showdown between Gus and Walt. These are two very smart men, and Gus, being the smarter, is always ahead. He has more eyes, more ears, and more experience. So you’ll have to see Walt get very, very tricky to even get in Gus’ presence.”