Witnesses who filmed and photographed Tony Scott's fatal leap from a bridge into Los Angeles harbour are reportedly hawking the footage to media outlets.

The material captures the British director crouching moments before he jumped an estimated 185ft to his death on Sunday. The show business website TMZ said it had seen – but not purchased – some of the footage.

Some witnesses said they assumed at first it was an extreme sports stunt, not a suicide. A surveillance camera from a nearby business also recorded the jump.

News of the macabre footage came as it emerged Scott made meticulous preparations for his death and had planned to use the bridge from which he jumped in a blockbuster film.

The 68-year-old left a list of contact names, numbers and instructions in his car for police to find after he jumped, one of several notes he left in various locations.

The most detailed note, which reportedly explained why he took his own life, was left in his office. Its contents were not immediately revealed, leaving his motives a mystery to the public as harrowing details emerged of his final moments.

ABC reported on Monday that the 68-year-old had inoperable brain cancer but hours later the theory was rebuffed by Craig Harvey, the coroner's department chief investigator. "A family spokesman told us late this afternoon that the information was not true, but we will be looking at everything," he told reporters. ABC quickly retreated from the story.

An autopsy had been completed but final results must wait six to eight weeks for toxicology tests, added Harvey.

The lack of obvious motive baffled commentators who said the British director of Top Gun, Crimson Tide and Beverly Hills Cop II appeared to have it all: success, wealth, respect, a wife and two young children.

His brother and production partner, Sir Ridley Scott, flew from London to Los Angeles as tributes continued flowing for the late director. Tom Cruise, who was planning to make a Top Gun sequel with Scott, said in a statement: "Tony was my dear friend and I will really miss him … My deepest sorrow and thoughts are with his family at this time."

Oliver Stone tweeted: "My favorite Tony Scott film is "Enemy of the State" (1998). Brilliant and way ahead of its time. Will miss him."

It emerged that Scott was very familiar with the Vincent Thomas bridge near Long Beach, about 30 miles south of his Beverly Hills home, because he planned to use it in a remake of the 1970 cult classic The Warriors, about a gang crossing New York to their Coney Island home pursued by rival gangs.

In a 2009 interview with the website Rotten Tomatoes Scott said he wanted to switch the story to Los Angeles because it was horizontal whereas New York was vertical.

He envisaged the climax of the film on the suspension bridge which spans the harbour. "I'm hoping to get 100,000 real gang members standing on the Vincent Thomas bridge for one shot. I've been meeting the various gangs as part of the research. I've met them all, Crips, Bloods, The 18th Street Gang, The Vietnamese and so on. They all love The Warriors, so it was, 'Yeah, fuck yeah, we'll be in that!"

Witnesses described the director's final minutes on a sun-drenched early afternoon. After parking his black Toyota Prius he made his way to a fence on the bridge's southern side.

"He was looking around and fumbling with something at his feet," David Silva, a car passenger on the northern side, told the Los Angeles Times. "He looked nervous. I thought it was some extreme-sports guy."