evidence: Acting ICE Director P.J. Lechleitner sent the data, collected as of July 21, as part of a request sent in March from Republican Rep. Tony Gonzales of Texas. [...] But the agency’s limited resources limit how many they can locate and arrest. There are currently more than 7.5 million immigrants on ICE’s "non-detained" docket, meaning they have pending immigration cases but are not currently in detention. [...] NBC News joined ICE agents in Maryland earlier this year when they arrested a man convicted of murder in Colombia and a man convicted of attempted murder in El Salvador.