At least three people were killed and nine injured Wednesday when a man driving a car at an indoor auto auction near Boston accidentally accelerated and plowed into a crowd. The driver has been identified as a man in his seventies, who wasn’t injured in the incident at LynnWay Auto Auction in suburban Billerica. Prosecutors say they believe it was a “tragic accident” and not a deliberate attack. One of the victims was identified late Wednesday as Leezandra Aponte, a mother of three who’d just started working at the auction center. Witnesses said the driver was lining up the Jeep Grand Cherokee on the auction block before it sped up abruptly and rammed into the crowd, only stopping after crashing through a concrete wall.