A white former police officer in a Dallas suburb was indicted by a grand jury on a murder charge for fatally shooting an unarmed black high school freshman in April with a high-powered rifle as the teenager and four others drove away from a house party, prosecutors said Monday.

The former officer, Roy D. Oliver II, an Iraq war veteran who was on the police force in the working-class city of Balch Springs, was also indicted on four counts of aggravated assault with a deadly weapon by a public servant.

The charges were announced by the Dallas County district attorney, Faith Johnson. If convicted of murder, Mr. Oliver, 37, could face a prison term of five to 99 years or life, the same range as the aggravated assault charges.

“These types of multiple charges against a police officer are historic in Dallas County,” said Daryl Washington, a lawyer for Jordan’s family in a lawsuit against Balch Springs and Mr. Oliver. “It sends a message to bad cops that you can no longer kill an unarmed person and get no billed.”