Anthony Pettis says his life -- and the lives of his family members -- were in immediate danger when his cars were set on fire Thursday morning ... and he vows retribution.
As we previously reported, cops are on the hunt for whoever went to the UFC star's Milwaukee home around 1 AM and torched 3 vehicles on Pettis' driveway in the middle of the night.
Pettis is now commenting on the seriousness of the situation -- "My life as well as my loved ones were put in danger. I cannot understand why someone would want to hurt myself or my family."
He adds, "I am grateful that no one was harmed by this cowardly act."
"I will do everything I can to ensure that we find out who committed this crime and that they are prosecuted to the full extent of the law."
Pettis is also reaching out to his neighborhood -- saying, "I really hope the city that I rep has my back on this one and helps by reporting anything they know about this."
"I will not be defeated."