Kirstjen Nielsen will go down in infamy for claiming the Trump administration did not “create a policy of separating families at the border,” but the man taking her job as homeland security secretary actually implemented the policy and it was his agents who did the separating.

Kevin McAleenan was the commissioner of Customs and Border Protection until Monday, when he was named acting secretary of the Department of Homeland Security after President Trump sacked Nielsen because he reportedly thought she wasn’t tough enough on the southern border. But McAleenan has been plenty tough on the border, with his agents apprehending thousands of migrants for criminal prosecution and turning away thousands more asylum seekers.

Yet he is being portrayed by some as a relative moderate, with many noting his service as deputy CBP commissioner during the Obama administration, which increased deportations and hardened immigration policy. McAleenan served admirably enough for President Obama to grant him an award because he achieved “extraordinary results” in his position.

“The fact that you served under Obama certainly doesn’t absolve you from any possibility of being a hard-right immigration enforcer,” said Matthew Kolken, an immigration attorney and frequent critic of both the Obama and Trump administrations’ immigration policies.

In April 2018, McAleenan co-authored a memo to Nielsen stating that DHS could “direct the separation of parents or legal guardians and minors held in immigration detention so that the parent or legal guardian can be prosecuted... ” The memo laid out several options for Nielsen to choose so DHS could help prosecute every unauthorized border crossing under the abandoned “zero tolerance” policy. Nielsen evidently chose the option that included widespread separation and signed her name to the memo.

Soon afterward, CBP was separating migrant parents from their children. More than 2,500 families were separated before the program was halted a year ago—and not all have been reunited.

In McAllen, Texas, CBP agents prevented parents from being reunited with their children, according to the DHS Office of Inspector General.

“CBP may have been able to avoid separating some families,” a 2018 OIG report states. “However, CBP officials later arranged to have adults transferred directly from court to ICE custody, rather than readmitting them where they might be reunited with their children. According to a senior official who was involved with this decision, CBP made this change in order to avoid doing the additional paperwork required to readmit the adults.”

Around the same time, CBP began turning away asylum seekers.

Agents stood at the dividing line between the U.S. and Mexico, preventing migrants from entering American territory where they are legally allowed to claim asylum, according to the Mexico Security Initiative at the University of Texas at Austin’s Strauss Center. Agents allegedly told them there was “no room” or that the U.S. wasn’t currently accepting asylum claims at that time (a blatant lie), according to UT-Austin.

More recently, McAleenan’s agents have been implementing the administration’s policy of sending asylum seekers back to Mexico to await their day in court, a policy known as “Remain in Mexico.” On Monday, a federal judge in San Francisco put a temporary stop to the policy, noting that the practice directly contradicts the “government’s acknowledged obligation to ensure aliens are not returned to unduly dangerous circumstances.”

It has been McAleenan’s CBP agents who have been sending migrants back to those “dangerous circumstances,” either in violent Mexican border towns like Tijuana and Juarez via Remain in Mexico.

It’s unclear whether Trump will nominate McAleenan to serve as permanent Homeland Security secretary as the White House “purges” the department. Meanwhile, immigrant advocates and attorneys are waiting to see what happens next. One thing is certain: McAleenan’s actions at CBP under Trump and Obama do not portend a softening of immigration policy at DHS.