I live on the Big Island and have spent literally hundreds of nights at the Marriott. It's not a long walk. I've made that walk dozens of times. It would be pretty dark because that night there was a quarter moon that rose about 3:30 in the morning so no moon at the time. The Marriott would be the closest place to go except Lava Lava. Even though they closed at 9:00 there would have been staff there cleaning up.I would expect authorities to wait for autopsy results before arresting him if the asthma was indeed true...they clearly have info that points to him.
The police know it is her body. They just are not saying it publicly until it is confirmed which will happen later today I'm sure. The husband has been arrested likely because they don't want him to leave the island. All of this is typical. If she actually died of an asthma attack, which can be confirmed by autopsy, case closed and they will release him. Otherwise there may be additional information released.