I am the worst mom ever

Tonight I was making dinner, my 3 1/2 yo and 9 month old (walking for a couple months now) were playing in his room. I had music going and had just checked on them.

The next minute I turned and looked and the screen door was open I ran to the door and didnt see them so I thought maybe l just hadnt shut it all the way, ran through the house calling my sons name then ran outside.

It was my worst nightmare, I thought I would pass out I couldn't see either kid!! I called out my sons name and then saw a flash out the corner of my eye and ran that way. My son was trying to play with the neighbor dog that had gotten out and my little baby had walked all the way past our lot and was happily trotting down the sidewalk into a neighbor I dont even know arms.

I had a full blown panic attack one I got inside. It all literally happened within seconds/minutes. Everyone is fine but I'm just riddled with guilt and what ifs. I just feel like the worlds shittiest mom tonight.