The power of the unknown.
That is a stupid bridge design . They should have a metal railing attached to the slant extending back and curved on the end.

No, this was divine intervention. It occurs through out the Bible. One that comes to mind is when Mary went looking for Jesus.

John 20:11-13
Mary stood outside the tomb crying. As she wept, she bent over to look into the tomb and saw two angels in white, seated where Jesus' body had been, one at the head and the other at the foot.
They asked her, "Woman, why are you crying?"
"They have taken my Lord away," she said, "and I don't know where they have put him."

Matthew 28:1-7
After the Sabbath, at dawn on the first day of the week, Mary Magdalene and the other Mary went to look at the tomb.
There was a violent earthquake, for an angel of the Lord came down from heaven and, going to the tomb, rolled back the stone and sat on it. His appearance was like lightning, and his clothes were white as snow. The guards were so afraid of him that they shook and became like dead men.
The angel said to the women, "Do not be afraid, for I know that you are looking for Jesus, who was crucified. He is not here; he has risen, just as he said. Come and see the place where he lay. Then go quickly and tell his disciples: 'He has risen from the dead and is going ahead of you into Galilee. There you will see him.' Now I have told you."

I firmly believe that that those cops heard the voice of a guardian angel that was sent down to protect that baby. It is not hard for me to believe because I have seen and been rescued from situations that I can't explain to this day.