My neighbor is a Church of GOD minister and some call them Pentecostals. He's a good man who has devoted lots and time and effort in service to The Lord. A church even the same denomination such as Church of GOD can be as different as night and day depending on the pastor and congregation. As well some members take things way too literally such as spiritual gifts and your faith will heal you and if not it's your fault etc. Most of their pastors however will not say this.
But the thread is about a tragedy. Who's to blame? I'm sure many feel some guilt. It sounds like a tragic accident. Sad to say we are in an imperfect world of imperfect humans and the family needs prayers.
A church function can be lots of things including a fellowship meal outside of the sanctuary itself usually in another large room. Doors locked to the Baptismal pool in some churches would not have stopped a child from say climbing over a choir seat and falling into the pool. Miscommunications of who has a kid also happen even in the best of circumstances. The teen watching the child may have thought an adult or parent had the child who knows. We weren't there.
The Toddler is home with The Lord that much we do know for certain. The child was not of the age of accountability and thus an innocent child.
I feel bad for the kid and the family. That being said Pentecostal churches are nuts. They create doctrine from inspiration and experience and emotion. Are they “dead” cyhurches? Yes. In their own very special way.