The department planned to hold another news conference Monday afternoon.
A representative for the church, Don Iloff, said he did not believe the shooter was known to members and leadership of the church.
At a news conference after the shooting, a beaming Mr. Osteen said he intended to continue his mission of providing hope.
“We don’t understand why these things happen but we know God’s in control,” said Mr. Osteen, who tends to avoid wading into politics. “There are forces of evil but the forces that are for us, the forces of God are stronger than that.”
The shooting took place around 1:53 p.m. on Sunday, after an English-language service had ended and as a Spanish-language service was beginning. The church occupies a stadium-size building along a major highway that was the former home of the Houston Rockets basketball team. Services draw tens of thousands in-person, and many more watch online and on television.