The woman, estimated to be between 30 and 35 years old, entered the megachurch shortly before 2 p.m. dressed in a trench coat and armed with a long gun and a backpack, Houston Police Chief Troy Finner said in a Sunday afternoon news conference.
https://www.cnn.com/2024/02/12/us/joel-osteen-lakewood-church-shooting-monday/index.html
Could be as you suggest.
So was this an 'assault backpack'?