Speed was a factor in the fiery crash that killed "Fast and Furious" star Paul Walker and friend, professional driver Roger Rodas, authorities said today, as Walker's father spoke out about his grief.

Related: Paul Walker's father recalls last talk with his son

Police got a phone tip after Saturday's deadly accident saying that another car had been at the scene of the accident, according to Sgt. Richard Cohen, a spokesman for the LAPD.

Authorities say they want to know whether that driver cut off Walker and Rodas. So far, however, police have been unable to reach the tipster. Cohen said investigators were looking for surveillance videos for clues.

Investigators say they are also looking into skid marks at the crash scene to find out whether they came from Rodas' car or someone else's.

Related: Paul Walker dead: Cause of crash under investigation

Walker's publicist Ame Van Iden said he was a passenger in the car as Rodas drove in the community of Valencia on Saturday. The two were leaving a fundraiser they'd thrown to benefit victims of the typhoon in the Philippines. Walker was 40; Rodas, 38.

They were just blocks from the event, in a business park, when the car they were traveling in - a 2005 Porsche Carrera GT - smashed into a light pole and tree. Both bodies were badly burned. Police said the impact of the crash was so great that a piece of the car flew into an nearby building and broke a window.

The 2005 Porsche Carrera GT is one of the fastest cars in the world. It sells for more than $400,000 and goes from zero to 125 mph in less than 10 seconds. It can also reach speeds of 205 mph. The Porsche Carrera GT is reportedly so difficult to handle that even professional drivers have called it scary.

Porsche said it was cooperating with the investigation.

Related: Inside Tyrese Gibson's emotional visit to Paul Walker's crash site

Paul Walker (Andrew Medichini/AP Photo)

Today, as fans continued to gather at a makeshift memorial near the site of the crash, Walker's father, Paul Sr., said he'd always told his son he loved him.

"I knew that eventually he might come to realize what a good person he was," Paul Sr. said. "We lost a spirit. … I'm devastated."

ABC News' Cecilia Vega, Maggy Patrick and Lawrence Dechant contributed to this article.