Suffolk County police have released surveillance video of the crash on Montauk Highway in Lindenhurst that killed Brittany Walsh.
The video shows Michael Grasing, 31, swerving in and out of traffic at about 85 to 100 miles per hour, police said. He then crashed into the back of Walsh's SUV, causing it to overturn several times and strike a utility pole, police alleged.
Walsh, 18, was pronounced dead at the scene.
Police arrested Grasing and charged him with DWI. His blood alcohol level was 0.30, nearly four times the legal limit, police said.
Authorities are asking witnesses, including one who may have had an interaction with Grasing just moments before the crash, to come forward.
"One eyewitness is at a light and overhears another operator of a motor vehicle actually yelling at the defendant to pull over, stop driving or he's going to kill somebody" District Attorney Thomas Spota. "That occurs within probably minutes of this horrific accident."
Walsh, an athlete and an honors student, had just graduated from Copiague High School on Friday.
The Suffolk County Police Department is asking anyone with information about this crash to call detectives at 631-854-8152.