Hi FrostByteVA,
It sounds like you entered Burst mode when you pressed and held your Take Picture button for several seconds on your iPhone.
Take photos and videos - iPhone
http://help.apple.com/iphone/8/#/iph1e767793c
Take Burst shots: (iPhone 5s or later) Touch and hold the Take Picture button to take rapid-fire photos in bursts (available while in Square or Photo mode). The shutter sound is different, and the counter shows how many shots you’ve taken, until you lift your finger. To see the suggested shots and select the photos you want to keep, tap the thumbnail, then tap Select. The gray dot(s) mark the suggested photos. To copy a photo from the burst as a separate photo in your Bursts album in Photos, tap the circle in the lower-right corner of the photo. To delete the burst of photos, tap it, then tap .
In the Photos app the burst images appear in a stack. When you tap on the stack, you can select which of the burst images you want to keep. The rest of the photos will be deleted. So, I would suggest managing the photos from within the Photos app.
Another alternative is to use the Image Capture application to delete images directly from the iPhone.
Image Capture: Transfer images and other items from your device
https://support.apple.com/kb/PH17894?locale=en_US
Regards,