The North Carolina teen who beheaded his mother on Monday was in the U.S. illegally and had been wanted by federal immigration officials, the U.S. Immigration and Customs Enforcement announced on Tuesday.

Oliver Funes-Machado, 18, killed his mother, Yesenia Funes Beatriz Machado at her house in Franklin County, N.C., around noon local time on Monday. He then called 911 to report the incident. Officers said when the first deputy arrived at the scene, Funes-Machado walked out of the house with a butcher knife and his mother's head in his hands.

"It was a gruesome scene. … I can't tell you how many wounds," Franklin County Sheriff Kent Winstead told WRAL.

The suspect, who is originally from Honduras and did not have legal permission to be in the U.S., has been charged with first-degree murder. Shortly after, ICE issued a detainer on Funes-Machado, which would ensure federal immigration agents are alerted and can pick him up from jail or prison if he makes bond.

"Given the charge ... the detainer would also apply at whatever point if/when he gets out of prison down the road. So either avenue. But the detainer does not preclude any criminal prosecution," Bryan Cox, spokesman for ICE in the southern region, told the Charlotte Observer.

The late-Beatriz Machado had had other younger children in the house at the time of the incident. Officials said it's unknown whether they were in the U.S. legally or not. None of the children were harmed during the attack.

The suspect will undergo a mental evaluation, though his attorney admits he has "some substantial mental health issues" and is "a pretty profoundly disturbed young man."