A rival gang?

According to my Google AI Overview, a "rival" is a competitor, someone who opposes or competes with another for the same goal or in the same field.

If someone says in their defense that they fear being killed by a "rival gang," it's an admission that they're indeed in a gang. Which gang are they in? That depends! Let's shorten this story. 

The guy who was here illegally and was deported to El Salvador appears to have hung out with MS-13 gang members. Guilty by association? Very likely! Here's a fact, MS-13 is a terrorist organization. The United States can deport anyone who is here illegally, whether they are in a gang or not according to United States immigration law. I will stop here.