Remove Object And Storage Angular Firebase

I am working on my first project in Angular and Firebase, I'm almost done.

I have a question on deleting objects using both. I have a service that will delete an object. The object has another object inside called "picture" that has 2 properties, key: string and url: string.

I want to make sure to also delete the file from storage when that object gets delete, I found this way that works, but I don't think it's the correct way to do it, specially because I get a TS Error:

"error TS2339: Property 'picture' does not exist on type '{}'."

Can anyone help me with that? Here is my delete method:

deleteEvent(id: string) {
        const obj = this.db.object(this.NODE + id);
        const getPic = obj.snapshotChanges().subscribe(
            (a) => {
                console.log(a.payload.val());
                this.storage.ref(this.NODE + a.payload.val().picture.key).delete();
            }
        );
        return obj.remove();
    }

I'd say you've got the gist of it. If the only thing that's bothering you is the Linting errors, you can use bracket notation instead of dot notation: this.NODE + a.payload.val()['picture']['key']... I might introduce some error handling in there in case things break.

On one hand, for a small improvement, I'd recommend against using a subscription just to get the data from the database one time. AngularFire2 has a method for that with less overhead setting up an observable/subscription, when it's just about to be deleted anyways. If I were doing it, I would write it something like:

deleteEvent(id: string)
{
    return this.db.database.ref(this.NODE + id).once('value').then( data => {
        console.log(data.val());
        return this.storage.ref(this.NODE + a.payload.val()['picture']['key']).delete().then( () => {
            console.log('Success!');
            return this.db.database.ref(this.NODE + id).remove();
        }).catch( err => {
            console.log(`Error deleting ${this.NODE + a.payload.val()['picture']['key']} from storage:`);
            console.log(err);
        });
    }).catch( err => {
        console.log(`Error obtaining /${this.NODE + id} from the database:`);
        console.log(err);
    });
}

*untested code

I'm a big fan of promises (as if you couldn't tell) and AngularFire2 uses them a lot - makes handling errors much easier.