A Bay Shore woman is demanding her brother's killer be caught nearly four months after the hit-and-run that took his life.

Mary Ellen La Fata says it has been a difficult last few months since her brother, 51-year-old Robert Donahue, was run down and killed in Deer Park at the corner of Deer Park Avenue and Grand Boulevard.

In late October, the driver who struck Donahue also side-swiped a white SUV a few blocks away and fled both scenes. As of today, no one has been arrested.

"The car was found that day around the corner from my mother's house, so we're just waiting," says La Fata.

Back in October, News 12 spoke to Donahue's mother Eileen. She said her son had schizophrenia and spent his days at a nearby library. She says he was killed while walking home from that library. She found out when he didn't come home at his usual time.

"We had to drive around looking for him, we had to ask the police on the street," says Eileen Donahue.

There were witnesses and surveillance cameras at the scene of the incident. La Fata contacted News 12 after becoming frustrated with how long it was taking for an arrest to be made.

A spokesperson for the Suffolk County Police Department say there is a potential suspect, that a truck involved has been impounded and they are awaiting more lab results.

"We want closure, we want to know what happened, just some kind of peace from it, how somebody can leave someone like that," says Eileen Donahue.