Filmmaker George A. Romero, considered by many as the father of the modern-day zombie movie, died at 77 on Sunday in his sleep following a "brief but aggressive battle with lung cancer," according to a statement to the Los Angeles Times provided by his longtime producing partner Peter Grunwald.

Romero is best known for his 1968 black-and-white indie zombie movie "Night of the Living Dead," which focused on complex, diverse characters, making it much more than just a monster movie.

Initially, critics deemed the film too gory. Variety called it an "unrelieved orgy of sadism." But it was the fans who understood that it was more than a mere horror film, and it went on to become one of the most profitable horror films made outside a traditional studio, grossing $30 million internationally.

Even the Library of Congress listed the film in the National Film Registry as "culturally, historically, or aesthetically significant " back in 1999.

Romero's "Living Dead" franchise continued with his films "Dawn of the Dead" (1978), "Day of the Dead" (1985), "Land of the Dead" (2005), "Diary of the Dead" (2007) and "Survival of the Dead" (2009).

Throughout his life Romero was vocal about how zombies should be depicted in TV and film. He said, "Zombies cannot run. Their ankles would snap. What did they do, go and join a spa the moment they rose from the dead? Gimme a break. They're dead."

Romero is also known for movies "The Crazies" (1973), "Martin" (1978), "Creepshow" (1982), "Monkey Shines" (1988) and "The Dark Half" (1993).

Romero's horror films influenced everyone from horror author Stephen King to filmmakers such as James Gunn, Eli Roth, Jordan Peele and Scott Derrickson, just to name a few.

"Shaun of the Dead" director Edgar Wright posted on his website about his admiration for Romero.

"It's fair to say that without George A. Romero, I would not have the career I have now," Wright wrote. "A lot of people owe George a huge debt of gratitude for the inspiration. I am just one of many."

"Guardians of the Galaxy" director James Gunn posted on Facebook on Sunday about Romero.

"Seeing 'Night of the Living Dead' as a child not only scared the living hell out of me, and made me forever jump at creepy children, but it was so incredibly DIY I realized movies were not something that belonged solely to the elites with multiple millions of dollars but could also be created by US, the people who simply loved them, who lived in Missouri, as I did, or Pennsylvania, as you did, or anywhere," Gunn wrote.

"I picked up an eight millimeter camera, mixed some Karo syrup with some red food dye to make blood, and began making movies -specifically, having my one brother eat my other brother onscreen, alive. I was eleven," Gunn continued. "That was the first moment of my film career, and it was spurned on because of you."

Not only did Romero portray zombies worthy of our nightmares and inspire filmmakers to make the horror they wanted on the big screen, he also addressed civil rights head on by making his main character and hero in "Night of the Living Dead" an African-American actor, who was clearly in charge of the group of survivors. The movie also tackled traditional family issues and other American social values. 

"Romero used genre to confront racism 50 years ago," "Hostel" director Eli Roth said on Twitter. "He always had diverse casts, with Duane Jones as the heroic star of 'Night of the Living Dead.' Very few others in cinema were taking such risks. He was both ahead of his time and exactly what cinema needed at that time. You can trace a direct line from 'NOTLD' to 'Get Out.' And Romero created the modern zombie. The infectious bite. Shoot the head. Everything."

Famous fans like "Halloween" director John Carpenter, horror author Stephen King, "Get Out" director Jordan Peele, "iZombie" actor Rahul Kohli, "Superbad" director Greg Mottola, actor and comedian Patton Oswalt, "Doctor Strange" director Scott Derrickson, were among the many famous fans who paid tribute to Romero on social media.

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