Houston immigration attorney Hugo Balderas-Ibarra demanded that ICE release his clients from the Montgomery Processing Center in Conroe as federal and county officials investigate the shooting that killed Lorenzo Salgado Araujo in Magnolia Park Tuesday. Balderas-Ibarra is representing Daniel Tirado Pantoja and identified his other client as Jose.

Jose Rojas, a 51-year-old Mexican national who has lived in the U.S. for decades, was among those detained, the Associated Press reported. Salgado’s brother Victor also was detained, according to League of United Latin American Citizens CEO Juan Proaño.

Balderas-Ibarra said he’s worried his clients may be pressured into signing documents authorizing their “voluntary departure.” The U.S. Department of Homeland Security did not immediately return a request for comment.

“It is extremely important that we preserve the integrity of this investigation,” Balderas-Ibarra said at a press conference on Friday. “That will all be out the window if they are deported.”

ICE said Salgado evaded arrest, rammed an agency vehicle and tried running over an ICE agent, but Balderas-Ibarra said the workers who were in Salgado’s van have an “extremely different” account. They told the attorney that an ICE agent was never standing in front of their vehicle, or even within a direct line of it, and their attorney accused ICE’s account of being false.

“I believe my clients are telling the truth,” Balderas-Ibarra said.

Balderas-Ibarra said he’s not aware that ICE has threatened his clients, but it remains a possibility as a known tactic by the agency. He said the case’s magnitude could also factor into potential pressure from ICE.

“They do threaten immigrants with deportation,” he said. “They threaten them with 10-year penalties. They threaten them with never being able to come back to the United States legally. This is just a tactic that they use in order to in order to expeditiously remove as many immigrants as possible.”

Staff writer Julián Aguilar and Ralph Green contributed reporting.