Robert Shipp was sitting in a West Virginia prison when his father got sick and slipped away in a Chicago hospital.

His father’s death in 2012 served as another reminder to Mr. Shipp, 46, of how thick the prison walls were and how much he had missed since he was 21, when he was sentenced to life in prison for selling crack cocaine.

This week, Mr. Shipp returned his ankle monitor to a halfway house and became a free man. He was one of 3,100 people released early from federal custody on Friday as part of the First Step Act, a bipartisan bill signed by President Trump in December that, among other things, increased sentence reductions for good behavior.

Even before that bill passed, Mr. Shipp had been scheduled to be released in November because of sentencing reform during the Obama administration.