"In view of our earlier decision not to file charges, we have referred this prosecution to the Pennsylvania Attorney General", Philadelphia District Attorney's office communications director Cameron Kline said in a news release.
Legal experts said a judge upholding a private citizen complaint after the district attorney's office declined to charge is unusual but not unheard of; a more surprising outcome, they said, would be the attorney general's office deciding to prosecute Bostian. Both charges are misdemeanors.
Neifield ordered the District Attorney's Office to charge Bostian with involuntary manslaughter and reckless endangerment in connection with the derailment, which also left more than 200 people injured.
Lawyer Thomas R. Kline, who had sought the private complaint on the Jacobs family's behalf, said the charges wouldn't have happened "had a courageous family, the Jacobs family, not stood up against the decision of a local prosecutor not to press charges".
Mr. Mongeluzzi added, "The Attorney General's bold, decisive action sends a loud and clear message that endangering the lives of rail passengers, crews and the public will not be tolerated in Pennsylvania, and should not be tolerated anywhere", said Mr. Mongeluzzi. The curve's speed limit was set at 50 miles per hour.
The train had left Philadelphia minutes before, heading toward NY.
Bostian has a personal-injury lawsuit pending against Amtrak.
Federal investigators said they found no evidence Bostian was under the influence of alcohol or drugs or that he had been using a cellphone at the time of the May 12, 2015, derailment of Amtrak train 188, en route from Washington to NY. However, the National Transportation Safety Board concluded that nothing struck his locomotive. Investigators say seven to nine of those minutes the engineer was listening to and participating in the radio conversations regarding other trains being hit with a projectile.
Victims' lawyers have questioned why Bostian would have sped up, rather than slow down, if he had been startled by something striking the train.
The order follows the Philadelphia district attorney's office announcement Tuesday that it would not file charges against Bostian, citing insufficient evidence.
"This is the second anniversary of a horrific event", Mongeluzzi said.
Court records list addresses for Bostian in New York City and in Somerville, Massachusetts, near Boston.
Bostian's attorney hasn't returned a call seeking comment.
As NPR's Merrit Kennedy reported in October, a federal judge approved a $265 million settlement between Amtrak and people affected by the crash.
The Amtrak complaint involves only the death of NY executive Rachel Jacobs, 39, who left behind a husband and 2-year-old son.