Gilgo Beach suspected serial killer identified by witness Dave Schaller in 2010

TMZ.com

Suspected Gilgo Beach serial killer Rex Heuermann could have been arrested in 2010 - 13 years before his arrest - if only the cops had taken a guy named Dave Schaller seriously.

Schaller, who appears in our latest documentary -- "TMZ Investigates: Gilgo Beach Serial Murders: Missed Warning Signs" -- was roommates with Amber Costello, one of the "Gilgo 4."

News day /James Carbone

In 2010, Amber, a sex worker, had an encounter with a man at her house...he was paying for a lap dance. Shortly after arriving, Amber called Dave, telling him the man was trying to rape her.

Dave quickly walked home, walked through the door and said he saw a giant man about 6ft 5in standing ominously in the living room. Dave told him to leave, and the guy refused. Dave ended up grabbing the guy, trying to pull him out, and a fight ensued.

Finally, the guy drove off in what Dave said was a green or black Chevy Avalanche.