Play video content EXCLUSIVE

Jenelle Evans' ex-fiance and second baby daddy called 911 not long after David Eason fatally shot her dog ... and it's crystal clear he was worried sick about his son's safety.

TMZ's obtained the 911 call and you can hear Nathan Griffith request cops do a welfare check because he'd just heard that Eason shot and killed Jenelle's French bulldog, Nugget. Nathan and Jenelle have a 4-year-old son named Kaiser ... who he believed was in the house at the time Nugget was killed.

Nathan said Jenelle had left the house after the shooting and gone to a friend's house -- but he was also concerned for her safety. He was speaking to someone in the room with him, and said if Jenelle goes back to the house -- where Eason was -- "somebody is going to die."

As we reported, Eason killed the dog with a shotgun after it nipped at the couple's 2-year-old daughter, Ensley. Eason also slammed Nugget against the back deck ... before firing the fatal shot.