Emile Hirsch ‘the troublemaker of Sundance,’ source says

Emile Hirsch is the talk of the Sundance Film Festival – for all the wrong reasons. His behavior has been so odd, he was dubbed by one festival insider the "troublemaker of Sundance 2015.”

The “Into the Wild” star is under investigation by the Park City, Utah police following accusations that he assaulted Paramount executive Dani Bernfeld at the Tao Nightclub in the early hours of Sunday morning.

According to the New York Post, the 29-year-old actor was “aggressively picking on” Bernfeld, and at one point pushed her up against a table and then “put her in a headlock.”

Paramount did not respond to a comment request.

Earlier that evening, Hirsch was seen urinating in an alleyway amid all the festivities happening on Main Street. He was also accused of questionable behavior while attending gifting suites throughout the weekend.

Hirsch attended the TR Suites, and we’re told he came in “with attitude,” refused to take his sunglasses off and left “in a huff” after being gently approached by a fan.

Another source said Hirsch visited the McCafe Village at the Lift twice during his time at Sundance, and both times kept completely to himself. “He stood in the corner and didn’t talk to anyone,” a witness said. “Not his castmates or reps or anyone. People were weirded out by him.”

The actor also hit up Kari Feinstein's Sundance Lounge, where again he kept to himself, apparently texting his co-star Hailee Steinfeld, even though they were in the same room.

Hirsch’s listed publicist and manager both told FOX411 that they were not currently working with the film star, and his agent and legal representative did not respond to a request for comment.

Hirsch was at the festival for the premiere of “Ten Thousand Saints,” also starring Ethan Hawke, Hailee Steinfeld and Emily Mortimer. Based on the novel of the same name, the film follows three lost kids and their equally lost parents as they come of age in New York's East Village in the era of CBGB, yuppies, and the tinderbox of gentrification that exploded into the Tompkins Square Park Riot of 1988.