A man charged with attempted murder for allegedly pushing a stranger onto the L tracks is free on bond after a family member Tuesday posted his $20,000 bond, jail officials said.

Chad Estep, 34, was arrested Monday and released about 9 p.m. Tuesday, about two hours after his attorney told Judge Michael Clancy that Estep, a Northwestern grad with a Ph.D. in neuroscience, could put up only about $5,000 to secure his release. Estep has worked as a data analyst since completing his doctorate this spring.

Prosecutors say Estep, unprovoked, pushed a 46-year-old man off the platform and onto the tracks at the Washington Blue Line station on August 1.

Chicago Transit Authority surveillance video and cellphone records showed that Estep was at the L platform at the time of the attack, Assistant State’s Attorney Erin Antonetti said Tuesday during a bond hearing at the Leighton Criminal Court House.

Judge Michael Clancy set bail at $200,000 for Estep, which required Estep to put up 10 percent of the amount to secure his release.

The victim, a 46-year-old man, had been waiting to board a train just before midnight at the station at 19 N. Dearborn St., after attending a Cubs game, when CTA surveillance video shows the man walking past Estep, prosecutors said. Estep can be seen leaning against a pillar and talking on his phone before the attack, prosecutors said, and cell phone records show Estep was near the platform and had been on his phone around the time the man was shoved.

The two men did not to interact until Estep “lined up” and shoved the victim onto the tracks, where he landed just inches from the electrified third rail, Antonetti said.

After shoving the man off the platform, Estep blocked him from climbing up from the tracks until good Samaritans on the platform managed to block Estep and help the victim off the tracks. Estep was identified by police based on anonymous tips and a comparison of still images taken from the surveillance footage and Estep’s picture on his online resume, Antonetti said.

After Estep was taken into custody Monday, he was identified by the victim, Antonetti said. Estep has no prior criminal record.

Tuesday, Estep’s attorney, Vadim Glozman, said he had “serious concerns” about how his client was identified as the attacker months after the attack.