A male Pittsburgh Regional Transit bus driver did not call police after a female passenger told him she had been sexually assaulted, choked and threatened with rape on his bus, according to a criminal complaint.

The 18-year-old woman sought help from another bus driver, who’s a woman. That driver called 911, locked the woman in the bus to protect her and got the license plate of the suspect’s vehicle, the complaint states.

PRT spokesman Adam Brandolph on Monday said he was unable to comment while a criminal case is pending.

The man charged with assault is Donovan Ivey, 25, of McKeesport. Transit police filed charges against him May 27 in connection with the May 23 incident.

Ivey had not been arraigned as of Monday, and there was an active warrant for his arrest, a court official said. He is charged with felony strangulation; misdemeanor counts of terroristic threats, simple assault and indecent assault; and a summary count of harassment.

According to the complaint, the woman told transit police that over the three previous months, she and Ivey had been talking through Snapchat and that they had met once before in West View. On May 23, she said, she had been at McDonald’s in West View for several hours when Ivey arrived. They both got on a bus near the restaurant.

The woman said that while waiting for the bus, Ivey tried multiple times to put her hand on his groin and forced her to drink vodka from a Gatorade bottle, the complaint states.

The woman said they got off the bus on Liberty Avenue in Downtown Pittsburgh and onto another bus. The woman said it was there, at the back of the bus, that Ivey sexually assaulted her and squeezed her throat to the point she had difficulty breathing, the complaint states.

That bus took them to the McKeesport Transportation Center. Before Ivey got off the bus, the woman said, he asked her, “What if I raped you while you were sleeping?”, the complaint states. When the woman said she would not like that, Ivey told her, “Doesn’t matter, I’m gonna do it anyways,” she reported to police.

After Ivey got off the bus and walked to his vehicle, the woman said she told the bus driver what had happened, but he did not call in the assault, the complaint states.

The woman got off the bus and onto another, which had a female driver. She told the female driver of the assault. That driver called 911 from her cellphone and locked the woman on the bus to protect her from Ivey. The driver got off the bus, read Ivey’s license plate as he drove past, and reported the details to 911.

McKeesport officers stopped Ivey in the 200 block of Fifth Avenue. He was detained and taken to transit police headquarters where police say he agreed to answer questions.

According to the complaint, Ivey admitted to kissing the woman but nothing else.

Ivey at first adamantly denied assaulting the woman. He later admitted to touching her thigh, which he said was consensual.

Asked if he had choked her, Ivey said he didn’t think he did, and later said he may have put his hands on her neck but did not apply any pressure, the complaint states.

Police said he continued to make “non-committal answers” to other questions about the woman’s allegations. Just before the interview ended, Ivey admitted to grabbing her breasts while they were kissing, according to the complaint.