It happened around 11 a.m. at Flower and Neighborhood roads in Mastic Beach.
Authorities say a Nissan Altima was traveling southbound on Flower Road when it apparently ran a stop sign and struck a Toyota RAV 4 at the intersection.
One of the vehicles overturned, and debris littered the crash area.
A woman, identified as 34-year-old Sabine Auguste, and a 2-year-old boy in the Altima were transported to a hospital for treatment of critical injuries. The driver of the Altima, who has not been identified, apparently left the scene.
Another passenger in the Altima, 33-year-old Jamel Hubbard, suffered non-life threatening injuries.
WATCH: Raw video from Newscopter7 over the crash scene
A woman named Stacey who lives next to the accident site and didn't want her last name used ran out of her house after the crash.
"Saw the guy come out from the car, holding the baby, baby was all limp," she said. "Everybody started screaming. The EMT started working on the baby."
Two people in the RAV 4 -- 59-year-old Maryann Valentin and 56-year-old James Mayo, were transported to the hospital for treatment of serious but non-life-threatening injuries.
A man who said his mother and stepdad were in the RAV 4 spoke to Eyewitness News and said his mom has broken back and broken shoulder, while his stepdad has six broken ribs. They were apparently on their way to look at a house at the time.
The Altima ended up crashing into Eric Sprague's Jeep in his driveway and his garage.
"I feel worse for the people that were in the vehicle than my own damages, because it's material," Sprague said.
The cause of the crash is under investigation.
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