Police are seeking help in finding the driver who killed a 13-year-old and injured another last week in Long Island, N.Y.

Suffolk County Sheriff’s Office did not immediately respond to PEOPLE’s request for comment.

Tyler and Krystal were both transported to Stony Brook University Hospital, where Krystalwas treated for a sprained arm, according to ABC 7. Tyler died several hours after the incident. His mother Desira Mack told NBC 4 that his skull and vertebrae were separated.

“He was a hero, he will always be a hero,” Desira told NBC 4, as Krystal added: “He saved my life.”

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Desira clarified to Westchester’s News 12 last Thursday that although her son was still on life support, he had no more brain function and was “not breathing on his own,” explaining: “The day they literally take him off everything is when he’s gone - but he’s already gone they said.”

Tyler and Krystal were walking home from Gordon Heights Children’s Park in a bike lane on Granny Road at around 7:30 p.m. when the car struck them from behind. Krystal told NBC 4 that the car had no lights on, even though it was dark outside.

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Family friend Steffani Campbell witnessed the incident in which the car “hit [Krystal] first and I guess [Tyler] went to jump and grab her, and it just took him,” telling NBC 4 that she “watched him fly to the middle of the street” before calling the ambulance and administering CPR.

Police believe the suspectdrove a dark-colored Chevrolet Equinoxmanufactured between 2005 and 2009, according to ABC 7. The front passenger headlight and bumper were reportedly damaged, and the passenger side mirror was broken.

Suffolk County Crime Stoppers is offering a $5,000 cash reward to anyone who calls 1-800-220-TIPS with anonymous tips leading to the arrest of a suspect.

A family member has since launched a GoFundMe campaign toassist Desira with funeral and burial costs. “My nephew was outgoing, adventurous, feisty yet kind, he loved with his whole heart for the ones he cared for, he was humorous, athletic etc. Tyler was an amazing kid!” the campaign reads.

source: people.com