A driver speeding down the road crashed into the back of a car carrying four family members at a Thornton intersection on Saturday night, killing all of them, according to newly released details from the Thornton Police Department's preliminary investigation. Daniel Daz, 22, and his brother Adam, 20, spoke with Denver7 over the weekend about the crash, which killed their parents and two younger sisters as they were headed to Walmart for groceries. The family had been stopped at a red light on northbound Washington Street at Thornton Parkway around 7:30 p.m. Saturday when the driver of a Subaru sedan, who was speeding northbound on Washington Street, struck the back of the family's Ford SUV, Thornton police said in a Tuesday morning news release.The crash caused the Ford's gas tank to rupture and catch fire, police said. Daniel said he received an SOS notification on his iPhone that his sister Nataly was involved in a crash.I get a message the notification on my phone saying that my little sister was detected in a crash," Daniel said. "That's when I ran out. I went to my car. I called my brother.When Daniel and Adam arrived at the scene, they saw the flames and quickly realized the worst."I was able to see my dad on the driver's seat," Adam told Denver7. "Once I saw he was there and he wasnt moving, that's kind of when I knew.Adam and Daniel told Denver7, their parents Francisco Daz and Beatriz Nez and their sisters 15-year-old Paola and 10-year-old Nataly were declared dead at the scene. The driver of the Subaru was taken to a nearby hospital with serious injuries, but Thornton police said there is still no update on the driver's condition. That driver has not been identified. A Chrysler van was also hit in the crash, but the driver was not injured. Thornton police traffic investigators continue to look into the crash. Anyone with information on what happened is asked to called the Thornton Police Department at 720-977-5150.If you'd like to help Adam and Daniel, their family has set up a GoFundMe page. They're hoping to raise $30,000 to provide the brothers with financial stability and emotional support.