The father of a Muslim-American soldier killed in Iraq who is caught up in a war of words with Republican presidential candidate Donald Trump is an immigration lawyer who specializes in a highly controversial program accused of letting immigrants buy their way into the U.S.

Khizr M. Khan’s website notes that he works to help clients with the E-2 and EB-5 programs that let overseas investors buy into U.S. companies and also provides green cards for family members.