SAN DIEGO -- A patrolman was legally justified in using a beanbag gun to subdue a combative, elderly San Ysidro man who died from his wounds a month later, District Attorney Bonnie Dumanis concluded in a ruling released Friday.

San Diego police Officer Carlos Ronquillo shot 87-year-old Guadalupe Zavala four times with the weapon -- which is designed to be non-lethal -- when Zavala came at him with a large shard of glass last Aug. 16, Dumanis wrote in a letter to San Diego Police Department Chief William Lansdowne.

Another officer then shot the octogenarian at his home with an electric stun gun.

Zavala, who suffered from dementia, pneumonia and chronic kidney disease, died in a hospital 30 days later of complications from blunt-force injuries inflicted by the beanbag projectiles.

Under state law, peace officers have the right to use lethal force to protect themselves or others from threats of death or great bodily injury, the district attorney noted.

"When Mr. Zavala ignored all commands and approached (police) in a threatening manner with a broken shard of glass, the officers were legally justified in discharging the beanbags and Taser at Mr. Zavala in an effort to protect themselves and one another," Dumanis wrote. "Accordingly, they bear no criminal liability for their actions."