OK, first of all, just watch this.
This shocking video is the work of the Connecticut nonprofit Sandy Hook Promise, which was set up after the 2012 Newtown massacre.
The PSA, released on Friday, is a part of the gun-violence prevention group's campaign called "Know the Signs."
"People who are at risk of hurting themselves or others often show signs and signals before an act of violence takes place," the Sandy Hook Promise website reads.
"When you don’t know what to look for, it can be easy to miss signs, or dismiss them as unimportant, sometimes with tragic consequences," it says.