Democratic members of Congress demanded answers about Homeland Security’s vetting and training of immigration enforcement agents after it was disclosed Thursday that the ICE officer involved in a deadly shooting this week in Maine had a history of mental health issues and violent behavior.

The Associated Press reported that David Brouillette, the Immigration and Customs Enforcement officer who shot a Colombian man in Maine, is an Army veteran who has struggled with serious mental health issues since early childhood, according to several of his close relatives.

The AP reached out to congressional leaders and several key lawmakers of both parties for response.

The top Democrat on the House Homeland Security Committee, Rep. Bennie Thompson of Mississippi, said Brouillette’s history of violence and mental health issues, as well as the death in Maine, “directly call into question the supposed vetting and training ICE does of its recruits.”

“This senseless tragedy must be investigated and the officer responsible should be taken off our streets and face justice for his actions,” Thompson said in a statement to the AP.