Countless warning signs were missed by law enforcement prior to the Florida high school shooter killed 17 innocent people — and the latest may be the most disturbing.

The New York Daily News released a video Friday of the alleged shooter standing in his backyard firing off a gun after a “practice”, months prior to the school shooting taking place. The gun appears to be an air-power pistol, not the AR-15 long rifle he reportedly used to shoot children at his former school.

The cellphone video, captured by a neighbor, is thought to be practice shots that adds on to the mountain of evidence that authorities missed.

The video shows the alleged shooter standing in his boxer shorts in a red hat firing off practice rounds and then placing the gun in his waistband before walking inside.

Watch the chilling video here —

Authorities have not yet disclosed a motive for the shooting.

Those who knew of the confessed shooter said he is a troubled and volatile teenager.

The FBI has already admitted that they failed to pass on credible evidence portraying the confessed shooter as a threat to the Miami FBI office. Documentation shows that more than 30 reports dating back to 2011 have been filed against the alleged shooter and his younger brother.

President Donald Trump has called the horrific failure of the FBI “unacceptable.”

Not only did the FBI drop the ball, local law enforcement and those who knew the alleged shooter could have helped prevented this horrible tragedy as well.

–The Horn editorial team