CHICAGO (CBS)–A Northwestern doctoral graduate has been sentenced to three years in prison after pleading guilty to pushing a stranger onto the Blue Line tracks last year.

Chad Estep, 34, of the Wicker Park neighborhood, pleaded guilty last week to aggravated battery.

Chad Estep (left) is charged with attempted murder for allegedly pushing Ben Benedict (right) off a CTA platform and onto the subway tracks below on Aug. 1, 2017. (Source: Chicago Police/Facebook)

An attempted murder charge, a second aggravated battery charge and a charge for unlawful restraint were all dropped.

Estep was accused of approaching Ben Benedict, 46, from behind at the Blue Line’s Washington Street station late on Aug. 1, 2017. He pushed him onto the tracks with both hands, knocking him close to the electrified third rail, prosecutors said.

Estep then tried to block Benedict from getting back onto the platform — and even tried to stop others at the station from assisting Benedict, according to prosecutors. Benedict managed to climb to safety seconds before a train arrived while Estep fled the station.

The two did not know each other, and a motive for the attack is unknown.

Estep earned his doctoral degree in neuroscience last year.