(NewsNation) — Former co-workers of Rex Heuermann, the man who is accused of killing six women, are speaking out about behavior they witnessed during work.

Mary Shell first worked with Heuermann in 2007 at an architecture firm that used the suspected killer as a consultant. Shell told NewsNation’s Ashleigh Banfield that she noticed Heuermann “hired a lot of women” when she worked directly for him. She’s now a journalist,

“Most of the staff were women. Myself, other colleagues, we might’ve been newer to the industry, less professional experience,” Shell said on “Banfield.” “I think that helped him maintain a certain power dynamic where he is training you, he’s signing your paychecks. He’s the boss. I’m sure that it inflated his ego.”

Jeffrey St. Arromand, Heuermann’s former associate, told “Banfield” that one of his female co-workers was “taken aback” by how “aggressive” their colleague was.

“The fact that he (Heuermann) wanted things done a certain way, and if you didn’t fall in line, he would let it be known that he was upset,” Arromand said. “Looking at all the details, this is one of the top architects in the country. … If that’s a microcosm of him wanting things done his way. … I’m not surprised, to be honest.”

During Heuermann’s latest court appearance Thursday, he was charged with the killings of two women, in addition to already being suspected in the deaths of four women found near Long Island’s Gilgo Beach.

According to a bail application released by Suffolk County District Attorney Ray Tierney, Heuermann faces additional second-degree murder charges for the deaths of Jessica Taylor and Sandra Costilla.

Since 2010, police have been probing the deaths of at least 10 people, most of whom are sex workers, whose remains were discovered along an isolated highway not far from Gilgo Beach. Victims had gone missing over a span of at least 14 years. 

Heuermann, an architect who lived across a bay from where the bodies were found, was arrested last July in connection to the killings of Megan Waterman, Melissa Barthelemy, Amber Lynn Costello and Maureen Brainard-Barnes.

At last week’s hearing, Heuermann pleaded not guilty to killing Taylor and Costilla and was ordered held without bail. Michael Brown, Heuermann’s attorney, told reporters afterward that Heuermann is “horrified by the new charges,” and “obviously in a bad place” regarding them.

NewsNation’s Laura Ingle contributed to this report.