Santa Clarita, California (CNN) -- The fire that engulfed the Porsche carrying actor Paul Walker apparently did not erupt until a minute after the car clipped a light pole Saturday.
That conclusion is based on security camera video obtained by CNN that shows black smoke starting to rise from the crash scene 60 seconds after it shows the light pole and a tree falling.
Could Walker and the other occupant in the car have made it out in those 60 seconds? That's hard to tell. The two may have died on impact when the car struck the light pole. The answer might be clearer when the coroner's office releases its preliminary findings of the autopsies of the remains of two men -- presumed to be Walker and friend Roger Rodas, a coroner's officer said.
The autopsies were completed Tuesday, Los Angeles County Coroner Lt. Fred Corral said. But investigators have placed a "security hold" on it for now.
The coroner will not even disclose if the identities have been confirmed using dental X-rays. Officially, the dead are only identified as case numbers.
Corral did not give a reason for the secrecy, which can be requested by law enforcement agencies during an investigation. It is often done in cases involving criminal probes, but there has been no indication this is anything more than a traffic accident investigation.
The autopsies should be able to confirm whether Rodas, as witnesses reported, was behind the wheel with Walker in the passenger seat.
Video obtained by CNN Tuesday from a security camera posted on a building on the opposite side of the street from the crash does not show the Porsche Carerra GT crashing along a business park street in Valencia, California, Saturday afternoon.
It does show the light pole and tree falling. Smoke is faintly visible above the scene 60 seconds later, followed by a heavy plume of black smoke after two minutes.
As investigators searched for more information about the accident that killed the popular "Fast & Furious" actor on Saturday, one of his co-stars dramatically addressed grieving fans.
Using a police car's loudspeaker, actor Vin Diesel thanked a crowd of mourning fans, calling Walker an "angel up in Heaven." Every night since the crash fans have gathered and left mementos near the spot on a wide business park road in Valencia, California, about 30 miles north of Hollywood, according to Walker's publicist and CNN affiliate KCAL.
Rodas, owner of a high-performance car shop, is believed to have been driving. Both Rodas and Walker were drivers for Rodas' Always Evolving racing team, according to the team's website.
By Tuesday Diesel had posted several pictures of his friend on his Facebook page.
And earlier this week, another co-star, Tyrese Gibson, broke down sobbing as he laid a yellow flower at the site.
Walker's father, Paul Walker Sr., choked back tears Monday. "His heart was so big," he told CNN affiliate KCAL. "I was proud of him every day of his life."
The actor had told his father that he wanted to take a hiatus from acting to spend more time with his 15-year-old daughter, Meadow, the elder Walker said. "And then boom, he got another movie. He would say, 'I don't know what to do.'"
He said the actor's siblings are having an especially hard time grappling with the death.
"I'm just ... glad that every time I saw him, I told him I loved him," the father said. "And he would say the same thing to me."
The Walker family issued a statement expressing thanks for "the outpouring of love and goodwill from his many fans and friends."
They asked that instead of flowers, people make donations to his charity, Reach Out Worldwide. The actor was at a benefit for the charity just before he died.
"It's comforting for them to know that the son, brother, and father they love so much is equally adored, respected, and appreciated by so many," the statement said. "Paul founded the organization with the genuine desire to help others, and it's important to his family to keep his memory alive through ROWW."
No memorial service plans have been made, Walker's publicist has said.
Meanwhile a Los Angeles County Sheriff's Office probe is focused on the speed of the 2005 Porsche Carrera GT, the spokesman told CNN.
Sheriff's Sgt. Richard Cohen told CNN that authorities received a tip Sunday suggesting that another car was at the scene racing the Porsche when it slammed into a light pole and burst into flames.
But investigators have since ruled out the presence of a second vehicle and the theory that the Porsche was drag racing, a spokesman said Monday afternoon.
But speed was a factor in the crash, the Los Angeles County Sheriff's Office said. A 45-mph speed limit sign was attached to the light pole knocked down by the Porsche.
The car, which sold for $450,000 when new, is a notoriously difficult vehicle to handle, even for professional drivers, according to Autoweek magazine. A top driver called it "scary," the magazine reported Sunday. It is powered by a V-10, 610-hp engine.
The wreck took place about 3:30 p.m. Saturday.
Antonio Holmes told the Santa Clarita Valley Signal newspaper that he was at the charity event when Walker and Rodas left for a ride in the Porsche.
"We all heard from our location," Holmes told the Signal. "It's a little difficult to know what it was. Someone called it in and said it was a vehicle fire. We all ran around and jumped in cars and grabbed fire extinguishers and immediately went to the vehicle. It was engulfed in flames. There was nothing. They were trapped. Employees, friends of the shop. We tried. We tried. We went through fire extinguishers."
Jim Torp, a car enthusiast who was at the charity event, said Walker was smiling as he got into the Porsche minutes earlier.
Torp thought he heard a blast in the distance before the car slammed into a light pole, he said. "What the first explosion was -- I don't know if their tire blew up, because it sounded like a tire blew on the car," Torp told CNN Monday.
Skid marks on the asphalt near the crash site, which indicate a car was doing doughnut spins, also are being examined, Cohen said. It's not uncommon for people to speed down that street, and two years ago deputies tried to crack down on that, he said.
Torp told CNN that he looked closely at the skid marks and concluded they were left by a car with smaller tires.
There are tales of Walker's incredible generosity.
CNN confirmed one story from a decade ago when Walker noticed a young U.S. soldier shopping with his fiancee for a wedding ring in a Santa Barbara jewelry store.
"The groom was just back from duty in Iraq, and he was going to be deployed again soon and wanted to buy a wedding ring, but he said he just could not afford it," saleswoman Irene King told CNN. "I don't think the soldier realized how expensive those rings are, about $10,000."
The couple apparently did not know who Walker was, King said.
"Walker called the manager over and said, 'Put that girl's ring on my tab,'" she said. "Walker left all his billing info, and it was a done deal. The couple was stunned. She was thrilled and could not believe someone did this."
King called it "the most generous thing I have ever seen."
The day Walker died he was at a holiday toy drive for Walker's charity hosted by the store that Rodas owned.
Walker and Rodas had planned Saturday as a day to help survivors of Typhoon Haiyan in the Philippines. The car shop website invited customers to a "Charity Toy Drive & Automotive Social Gathering."
"During the holiday season, many economically disadvantaged children from around the world are faced with the same dilemma year after year; the lacking of joy and cheer," the invitation read. "Our goal here is to be able to provide aid to these less fortunate children in hopes of helping them grow up to become confident, responsible and productive young adults."
Box office success
Walker's career began on the small screen, first with a commercial for Pampers when he was 2, and then with parts in shows such as "Highway to Heaven" and "Touched by an Angel."
His first few movie roles were as supporting characters in teen flicks, most notably in "Varsity Blues." But his career really took off when he was cast as undercover cop Brian O'Conner infiltrating a street-racing gang in 2001's "The Fast and the Furious."
The box-office success of the surprise summer hit yielded numerous sequels. And along with Vin Diesel, Walker was one of the franchise stalwarts. The six "Fast & Furious" films sold a total of $2.6 billion in tickets worldwide, according to BoxOfficeMojo.
Walker wasn't just a car enthusiast on the silver screen; off screen, the actor competed in the Redline Time Attack racing series.
On his verified Twitter account, Walker described himself as an "outdoorsman, ocean addict, adrenaline junkie ... and I do some acting on the side."
Walker also is the star of "Hours," an independent film scheduled to be released December 13 about a father struggling to keep his newborn infant alive in the aftermath of Hurricane Katrina in New Orleans.
Future of franchise
Walker was in the middle of the seventh film in the "Fast & Furious" franchise. The film was due out next year.
It's unclear how the movie's production might proceed. When Oliver Reed died in the middle of the production of "Gladiator," the rest of his scenes included a digitally produced image of his face on another actor's body, Tom O'Neil, editor of the show business website Goldderby.com, told CNN.
In some cases, other actors have filled in for co-stars who have passed away.
"We don't know what they'll do here, or even if they'll just say, "It may be tasteless to proceed at all because we can't be showing Paul Walker in a speeding car, defying death in a movie that ended up being the way he died,'" O'Neil said.
CNN's Alan Duke reported from Santa Clarita, and Ashley Fantz from Atlanta. CNN's Holly Yan contributed to this report.