According to video tape reviewed by Baltimore police, Mitchell put on the vest, looked into the camera and said he was ready to take a "deuce deuce in the chest."
Ramiro missed Mitchell's vest and instead shot him with a .22 caliber handgun.
Ramiro and the third person rushed to help Mitchell, and drove him to the hospital. Mitchell was declared dead a few minutes after they got to the hospital, according to police.
Officers were then called to the hospital and obtained a warrant for the video tape that captured the incident, according to the Baltimore Sun.
A spokesman for the Maryland attorney, Mark Cheshire, told the Baltimore Sun that prosecutors originally sought a second-degree murder charge, and the court commissioner later added the first-degree charge.
In May, a South Carolina man died after a friend allegedly missed his bulletproof vest while testing the body armor. Taylor Ann Kelly was charged with involuntary manslaughter after the incident.
Image via WBAL-TV