The Department of Justice has opened a criminal investigation into the conduct of an embattled Calumet County district attorney accused of “sexting” a domestic abuse victim, a DOJ official confirmed Friday.

DA Ken Kratz, 50, has admitted to sending a series of inappropriate text messages to Stephanie Van Groll, 26, while he was prosecuting her ex-boyfriend for trying to strangle her.

Three other women have also come forward claiming Kratz misused the authority of his position by attempting to spark a romantic relationship with them, including one woman who said Kratz sent her sexual text messages while he was helping her seek a pardon for a prior drug conviction.

Justice official Kevin Potter confirmed in a letter to the Associated Press the Division of Criminal Investigation has opened a probe into Krazt’s conduct, which could result in criminal charges.

The Office of Lawyer Regulation also reopened its investigation into Kratz’s behavior Sept. 24 and could move to remove Kratz’s law license.

The OLR investigated Kratz after Van Groll filed a complaint with the police but ultimately found he had committed no misconduct and closed the investigation in Nov. 2009 without forwarding the complaint to the DOJ.

Potter previously criticized the office’s investigation of Kratz in a letter and urged the office to reexamine the issue.

The DOJ’s confirmation came on the same day Van Groll filed a lawsuit in U.S. District Court in Milwaukee against Kratz, alleging he violated her constitutional rights.

“Kratz’s latest victim blew a whistle and no one listened. This lawsuit will provide (Van Groll) with the hearing she never received,” Michael Fox, Van Groll’s attorney, said in a statement.

Van Groll’s lawsuit alleges Kratz sent her the text messages because she was a young woman, which violated her right to equal protection under the law regardless of sex or age.

The lawsuit also claims Kratz used similar tactics on another domestic abuse victim 10 years ago, including telling the woman “he could have a dominatrix from Chicago with whom he was familiar train the victim/witness to be more submissive to his advances”.

Van Groll’s lawsuit seeks unspecified damages for the alleged harm caused by Kratz’s actions.

Kratz resigned Oct. 4 and is currently seeking treatment for an undisclosed condition at an undisclosed location outside Wisconsin.