Louis Johnson, 28, is charged with criminal sexual assault and public indecency/lewd exposure. View Full Caption DNAinfo; Chicago Police Department

COOK COUNTY CRIMINAL COURTHOUSE — A Hyde Park woman was knocked down and raped during a run on the Lakefront Trail in the Oakland neighborhood about 6 p.m. Sunday, prosecutors said.

Louis Johnson, 28, is accused of grabbing the 27-year-old victim by her knees and pushing her toward some trees near the trail in the 3500 block of South Lake Shore Drive.

As the woman struggled and tried to get away, Johnson pinned her down by the neck and said, "Be quiet or I'll kill you," according to an arrest report.

Johnson then pulled down the victim's leggings and underwear before removing some of his own clothing and sexually assaulting her, Assistant State's Attorney Ed Murillo said during a bond hearing Tuesday.

After several minutes, Johnson ran away, prosecutors said.

A witness saw Johnson pull up his pants and run off without a shirt, leaving the victim partially clothed on the ground, Murillo said.

The woman immediately cried out to the witness, who called police.

Officers searching the area soon found Johnson, who had been described as a black man with dark skin and dreads who was wearing a dark jacket with orange around the neck and no shirt, according to prosecutors.

While Johnson was in custody at the Wentworth District police station, at 5101 S. Wentworh Ave., he placed his hands in his pants and moved his genitalia around while staring at an officer, Murillo said.

The victim was taken to the University of Chicago Medicine, where a rape kit was collected.

Police recovered a black T-shirt from the site of the attack, prosecutors said. Johnson was spotted on police surveillance video near the scene at the time of the attack.

Johnson, of the 4400 block of West Van Buren Street, is charged with aggravated criminal sexual assault and public indecency/lewd exposure.

According to state records, Johnson is on parole for burglary. He was released from prison in October and was expected to complete parole by 2018. Johnson also has prior convictions in several drug cases.

Cook County Judge Laura Sullivan on Tuesday set bail at $400,000.