Boston Celtics reserve guard Jabari Bird not only allegedly choked his girlfriend more than a dozen times during a reported act of domestic violence in September, but also repeatedly threatened to kill her, according to court documents made public Wednesday.

The documents were released after Bird, 24, pleaded not guilty in Brighton Municipal Court to two new counts of witness intimidation and threatening to commit a crime stemming from the same September incident.

Bird was arraigned in September on charges of assault and battery on a household or family member, assault and battery with a dangerous weapon, kidnapping, and strangulation or suffocation. He pleaded not guilty.

The two new counts are based on an interview the alleged victim had with Boston police on Sept. 13. According to a police report filed in court, the woman quoted Bird as telling her “if you don’t stop talking I’m going to kill you.“ And while kicking her during the attack he also allegedly said, “tell anyone about this, I don’t care where you are I’ll find you and I’ll kill you.’’

The woman, a student athlete at a local college, was in court during Wednesday’s hearing. Prosecutors said she has requested privacy. She had no interaction with Bird during the proceedings.

Bird’s lawyer, Brian T. Kelly, a partner at Nixon Peabody, commented briefly after the arraignment.

“We are hoping to resolve this soon. It’s a very unfortunate situation for everybody involved,’’ said Kelly, a former federal prosecutor best known for winning a conviction in gangster James “Whitey’’ Bulger’s 2013 racketeering trial.

Kelly declined to elaborate on the desired resolution in the Bird case. Bird did not speak to reporters on Wednesday.

The alleged attack on the woman occurred Sept. 7 inside Bird’s Brighton residence, the authorities said. Court records show the woman told police that she and Bird, who battles “anxiety issues,’’ began arguing in his apartment around 1 p.m. that afternoon over trust issues Bird was having with her.

She alleged he launched into a long, violent attack, choking her approximately 12 times and releasing her neck whenever she began to go limp, allowing her to catch her breath before resuming the assault.

Eventually, the woman told police, she passed out and woke up under Bird’s bed. He allegedly began kicking her when she poked her head out. At one point he dragged her away from the door to prevent her from leaving, the report said. The encounter took a turn when Bird started displaying “seizure like’’ symptoms and fell, according to legal filings. His girlfriend “picked him off the ground’’ and put Bird on a bed, where he fell asleep, the report said. She then left the apartment.

Police also noted Celtics trainer Art Hornecalled 911 around 9:40 p.m. that night after he got a text message from the woman. She had sent Horne a screenshot of Bird’s threat to kill himself if she didn’t return to the apartment, the report said. Horne went to Bird’s home to check on him and called 911, the report said.

In a statement after Bird’s September arraignment, the Celtics said the team “deplores domestic violence of any kind, and we are deeply disturbed by the allegations.’’

“Most importantly, our thoughts are with the victim of this incident,’’ the team said.

The Celtics said that under league policy, such matters are handled by the NBA office, not the team, “so the Celtics will be working with both the league and local authorities to assist in their ongoing investigations.’’

An NBA spokesman at the time said the league was “conducting a full investigation of the matter.’’ Asked to comment Wednesday, the league referred a reporter to the earlier statement, adding only that “the investigation is ongoing.’’

Bird released a statement hours after the September arraignment saying he was stepping away from the team.

“I’m taking some time away from the team as I deal with my legal and medical issues,’’ Bird said, apologizing “for the unnecessary distraction that I have caused’’ and saying “I do not condone violence against women.’’

Gary Washburn, Adam Himmelsbach, and Milton J. Valencia contributed. John R. Ellement can be reached at john.ellement@globe.com. Travis Andersen can be reached at travis.andersen@globe.com.