In Texas, the age of consent is 17. What he did was wrong, but it wasn't a crime in Texas.
To the best of my knowledge:
In Arizona, California, North Dakota, New York, Oregon, Virginia, and Wisconsin, it would have been a crime.
In Florida, Delaware, and Idaho, Utah, the age of consent is 18, but he was under the age of 24, which would have made it legal.
In Illinois, Michigan, Minnesota, New Hampshire, and New Jersey, the age of consent is normally 16, but his position as a youth group leader might have bumped the age of consent up to 18, making it a crime.
In other states, it would have been legal.
The law seems remarkably complex. And there seems to be lobbying both to increase and to decrease the age of consent.