LOS ANGELES, United States, June 4, 2025 (BSS/AFP) - The family of a man suspected of attacking a Jewish protest march with Molotov cocktails in the US state of Colorado was being held by immigration officials Tuesday, the government said.

Kristi Noem, Homeland Security Secretary, said the wife and children of Mohamed Sabry Soliman had been detained.

"We are investigating to what extent his family knew about this heinous attack, if they had knowledge of it, or if they provided support to it," she said.

Criminal investigations are typically carried out by the FBI and local law enforcement, not by the Department of Homeland Security.

Soliman's immigration status has been at the center of President Donald Trump's administration's response to the attack in the city of Boulder on Sunday, in which 12 people were injured.

Officials were quick to say he was in the United States "illegally" having overstayed a tourist visa.

But they also acknowledged he had applied for asylum and had been granted a work permit.

The White House took to social media, appearing to taunt the family.

"Six One-Way Tickets for Mohamed's Wife and Five Kids," the official account posted on X.

"Final Boarding Call Coming Soon."

Secretary of State Marco Rubio on Monday pledged to rid the US of "terrorists" who were in the United States temporarily on visas.

State Department spokeswoman Tammy Bruce on Tuesday echoed that sentiment.

"This heinous attack is a reminder that the decisions about who we let into this country and who we allow to stay is of vital national security and personal security importance to this country and of Americans everywhere," she said.

Soliman is due to appear in court in Colorado on Thursday. He is expected to formally face federal hate crime charges, as well as state charges of attempted murder.

He is suspected of throwing flammable liquid at a group of older people marching to raise awareness of the Israeli hostages still being held by Hamas after the October 7, 2023 attacks.

Investigators said he had with him an improvised flamethrower made from a backpack weed sprayer filled with gasoline.

In one video that purportedly shows the attack, a shirtless man holding bottles in his hands is seen pacing as the grass in front of him burns.

He can be heard screaming "End Zionists!" and "They are killers!" towards several people in red T-shirts as they tend to a person lying on the ground.