A Houston neighborhood has been on high alert for the last three days, as police continue to search for the gunman who shot and killed 7-year-old Jazmine Barnes as she rode in her mother's car with her three sisters Sunday morning. The sheriff has released a grainy image of the suspect's truck and said police are examining area security videos as leads pour in.

"I'm very confident, and we will not rest until an arrest is made. We are going to continue to search for this killer," said Harris County Sheriff Ed Gonzalez.

Jazmine Barnes. Harris County Sheriff's Office

The second grader was full of life. Her family called her Jazz, and said she was a happy 7-year-old who wanted to be a teacher.

Jazmine's teenage sister said the shooter was a white man with a beard, a description that has raised questions about whether the seemingly unprovoked attack was racially motivated. The sheriff said they haven't ruled out any motive.

"We're doing everything possible and then some to make sure we bring this killer to justice," Gonzalez said.

Jazmine's mom LaPorsha Washington was also hit by gunfire. She spoke to CBS News before she was released from the hospital Tuesday night.

"I haven't even seen her yet. Her father hasn't seen her yet. He didn't even want to go see her because he wanted to remember her as she was, not as what this man has left us," she said.

She believes it's only a matter of time before the shooter is caught.

"We're going to bring justice to my baby," Washington said.

A sketch of the shooter could be released as soon as Thursday.