The SRU constables are shown bunching up in the doorway and are then shot by the gun thugs. Special response teams do not bunch up as was shown when entering a building.
After Aidan is shot and Clara picks him up, he tries to go in the direction of the shooters but she walks him in the opposite direction. He had entered from that direction, so they had a clear escape path, yet they are then shown as being trapped in the building.